U.  C  D.  L1B7.ARY 


CALIFORNIA  STATE  MINING  BUREAU. 

A.  S.  COOPER,  State  Mineralogist. 


Bulletin  No.  16.  San  Francisco,  December,  1899. 


^ 


The   Genesis  of  Petroleum   and 
Asphaltum  in  California. 


By  A.  S.  OOOPBR,  State  Mineralogist. 


SACRAMENTO: 
A.  J.  JOHNSTON    :     :     :    superintendent  state  printing. 

1899. 


U  J^^lijB&ITI^e..xl  j:j|i'«  •>. 


€ENESIS  OF  PETROLEUM  AND  ASPHALTUM 
IN  CALIFORNIA. 


By  a.  S.  cooper,  State  Mineralogist. 


It  can  be  tentatively  stated  that  fossil  bitumens  are  princi- 
pally derived  from  terrestrial  and  marine  vegetation,  deposited 
in  sedimentary  strata,  then  changed  to  carbonaceous  matter, 
and  afterwards  distilled  by  the  heat  of  metamorphism. 

In  other  words,  the  bitumens  are  Nature's  coal  oils  and  tars 
distilled  in  Nature's  still,  generally  with  infinite  slowness  when 
compared  with  a  modern  tar  still  or  retort. 

Although  some  of  the  hydrocarbons  can  be  produced  syn- 
thetically in  the  laboratory,  still  it  is  to  be  believed  that  nearly 
all,  if  not  all,  of  the  accumulations  of  fossil  hydrocarbons  owe 
their  existence  to  the  vital  principle  that  they  are  derived 
directly  or  indirectly  from  organized  beings — animal  or  vege- 
table, probably  the  latter,  for  reasons  given  hereafter. 

In  the  decomposition  of  vegetable  tissue,  when  air  is  wholly 
or  partially  excluded  from  it,  as,  for  example,  when  buried  in 
the  ground,  the  constituent  elements  of  the  vegetable  tissue 
re-arrange  themselves  mutually  into  new  products,  either  with 
or  without  the  co-operation  of  the  elements  of  water,  the 
oxygen  gradually  uniting  with  the  carbon  to  form  carbonic 
acid,  which  separates  and  leaves  as  a  residue  substances  rich 
in  carbon  and  hydrogen.  It  is  in  this  way  that  bituminous 
coal,  peat,  and  brown  coal  (lignite)  have  been  formed  from 
vegetable  matter. 

With  carbonaceous  material  in  the  same  deposit,  the  same 
series  of  strata,  or  in  the  same  stratum,  there  are  differences  of 
composition.  The  varieties  of  carbonaceous  materials  may 
have  been  produced  from  different  kinds  of  plant  form,  from 
which  coal  has  been  derived,  and  the  peculiar  conditions  of  the 
districts  where  the  plants  flourished  before  their  downfall  and 
inhumation  or  submersion.     The  changes  that  have  taken  place 


c. 

H. 

0. 

52.65 

5.25 

42.10 

60.44 

5.96 

33.60 

66.96 

5.27 

27.76 

74.20 

5.89 

19.90 

76.18 

5.64 

18.07 

90.50 

5.05 

4.40 

92.85 

3.96 

3.19 

4  CALIFORNIA    STATE    MINING    BUREAU. 

in  the  original  plants,  during  their  passage  from  woody  fiber 
into  coal,  are  ascribed  to  evolution  of  a  part  of  their  hydrogen 
and  oxygen,  as  there  are  less  of  these  elements  in  coal  than  in 
wood.     This  will  be  observed  by  viewing  the  following  table: 

Organic.  Formation. 

Wood Recent 

Peat Recent 

Lignite Cretaceous  and  Tertiary  -.. 

Brown  Coal Cretaceous  and  Tertiary... 

Coal _:Secondary 

Coal ..Older 

Anthracite Crystalline 

Graphite Crystalline  and  Archaean...     100.00        

There  is  no  strict  line  of  demarcation  between  the  above- 
named  organic  matter;  the  one  below  gradually  merges  into 
the  one  above. 

The  older  the  formation,  the  greater  the  amount  of  carbon 
contained  in  the  coal,  the  amount  of  hydrogen  and  oxygen 
having  been  diminished.  This  fact  may  be  ascribed  chiefly  or 
in  part  to  the  degree  of  heat  and  pressure  to  which  the  lower 
and  older  coal  strata  have  been,  and  still  are,  subjected. 

Graphitic  and  anthracitic  varieties  of  coal  are  metamorphic 
coal  produced  by  heat,  the  volatile  matter  being  vaporized, 
which,  probably,  afterwards  condensed  in  fissures  and  porous 
rock  above,  as  bitumen,  petroleum,  etc. 

Graphite  occurs  in  the  Archaean,  but  none  of  the  other  coals 
are  found  in  these  rocks;  neither  is  bitumen  or  petroleum  oil 
found  in  the  Archaean  formation,  but  thej^  are  found  in  all 
the  other  formations  lying  above  the  Archaean.  From  this  it 
would  seem  that  the  bitumens  originated  in  or  above  the 
Laurentian  rocks,  and  not  below  them.  The  absence  of  the 
bitumens  and  petroleums  in  the  Archaean  formation  is  evidence 
against  the  theory  that  petroleums  are  produced  by  the  action 
of  water  upon  red-hot  carbonized  iron  in  the  interior  of  the 
earth.  It  is  at  least  conclusive  evidence  that  this  process  is 
not  at  present  in  operation. 

Graphite  is,  in  all  probability,  the  ultimate  stage  in  the  series 
of  changes  which  vegetable  matter  undergoes,  passing  through 
the  conditions  of  heat,  lignite,  and  mineral  coal,  to  end  in 
graphite.  Several  modifications  of  graphite  may  be  produced 
artificially.  When  cast-iron  is  melted  with  an  excess  of  char- 
coal, it  dissolves  a  portion  of  the  carbon.     This  carbon,  when 


THE    GENESIS   OF    PETROLEUM    AND    ASPHALTUM.  5 

the  iron  is  allowed  to  cool,  slowly  crystallizes  out  in  the  form 
of  large  and  beautiful  leaflets  of  graphite. 

Anthracitic  varieties  of  coal  are  associated  with  folded  and 
metamorphic  rocks.  Anthracitic  condition  of  coal  may  some- 
times be  traced  to  local  effect  of  igneous  rocks.  As  rocks  grow 
less  and  less  metamorphic,  the  more  bituminous  is  the  coal 
contained  in  them. 

Graphite  is  disseminated  in  strings,  veins,  and  beds  through 
hundreds  of  feet  of  the  lower  Laurentian  strata,  and  its  amount 
is  calculated  to  be  equal  in  quantity  to  the  coal  seams  of  an 
equal  area  of  the  carboniferous  rocks. 

In  Central  Scotland,  where  the  coal  fields  have  been  so  abun- 
dantly pierced  by  igneous  masses,  petroleum  and  asphaltum  are 
of  frequent  occurrence,  sometimes  in  chinks  and  veins  of  sand- 
stone and  other  sedimentary  strata,  sometimes  in  the  cavities 
of  the  igneous  rocks  themselves.  In  West  Lothian,  intrusive 
sheets,  traversing  a  group  of  strata  containing  seams  of  coal 
and  oil  shale,  have  a  distinct  bituminous  odor  when  freshly 
broken,  and  little  globules  of  petroleum  may  be  detected  in 
their  cavities.  In  the  same  district,  the  joints  and  fissures  of 
a  massive  sandstone  are  filled  with  solid,  brown  asphalt,  which 
the  quarry-men  manufacture  into  candles. 

Graphite  has  probably  the  same  vegetable  origin  as  mineral 
coal.  It  is  now  generally  conceded  to  be  of  organic  origin,  the 
result  of  metamorphism  of  some  of  the  products  of  destructive 
distillation  of  vegetable  tissues.  In  general  arrangement  and 
microscopic  structure,  the  layers  of  graphite  correspond  fre- 
quently with  coal  and  some  bituminous  deposits. 

The  majority  of  coal  mines  in  California  are  in  the  cretaceous 
rocks  and  the  lower  tertiary.  The  rocks  underlying  the  tertiary 
formation  and  in  the  lower  parts  of  the  tertiary  formation  are  in 
many  instances  metamorphic,  the  cretaceous  and  tertiary  rocks 
having  been  changed  to  metamorphic  rock  by  hydrothermal 
action,  and,  if  they  contained  carbonaceous  material,  petroleum 
was  distilled,  which  ascended  in  a  vaporous  condition  and  was 
condensed  in  the  unaltered  rocks.  After  condensation,  it  was 
carried  upwards  by  gas  and  hydrostatic  pressure,  and,  in  some 
instances,  by  rock  pressure. 

The  presence  of  nitrogen  in  the  California  petroleum  oils  has 
been  adduced  as  a  proof  that  they  are  of  animal  origin;  this 
proof  is  not  conclusive,  as  most  all  of  the  coals  and  carbon- 


6  CALIFORNIA    STATE   MINING    BUREAU. 

aceous  shales  yield  nitrogenous  products  when  subjected  to 
destructive  distillation.  As  a  proof  of  the  animal  origin  of 
petroleum,  it  has  been  stated  that  pools  of  petroleum  have  been 
found  which  were  filled  with  live  maggots. 

Many  hundreds  of  pools  of  petroleum  in  California  have  been 
examined  without  discovering  any  maggots  or  other  forms  of 
life  in  them,  although  there  have  been  swarms  of  flies  and  other 
insect  life  in  their  neighborhood.  In  the  vicinity  of  pools  of 
petroleum,  flies  quickly  discover  and  lay  their  eggs  on  spoiled 
or  moist  foodstuffs,  meat,  decaying  meat,  meat  broths,  dead 
animals,  in  manure  heaps,  etc.  Taking  into  consideration  the 
persistency  of  flies  to  deposit  their  eggs  upon  anything  capable 
of  sustaining  the  life  of  their  young,  it  is  to  be  believed  that  all 
pools  of  petroleum  would  be  filled  with  maggots  if  flies  were 
present  and  petroleum  was  a  suitable  food  for  their  larvae. 

Maggots  feed  upon  animal  and  vegetable  tissues  and  liquids, 
and  not  upon  their  fats  and  oils. 

When  animal  hydrocarbons  are  deprived  of  all  animal 
tissues  and  liquids,  they  are  not  molested  by  flies.  Petroleum 
is  also  found  to  be  an  excellent  maggot-killer. 

There  are  only  four  ways  of  preserving  animal  remains  from 
decay  and  putrefaction:  first,  in  a  case  from  which  the  air  has 
been  completely  removed  and  excluded;  second,  by  antiseptic 
agents;  third,  subjected  to  a  heat  exceeding  100°  C;  fourth, 
subjected  to  a  cold  under  0°  C. 

To  secure  and  preserve  any  quantity  of  animal  remains  by 
any  of  these  four  ways,  cataclysms  of  nature  must  occur. 
Geology  does  not  show  that  any  large  quantity  of  animals  have 
been  inhumed  in  the  earth  by  cataclysms;  even  provided 
animals  were  buried  in  this  manner,  there  is  sufficient  oxygen 
present  to  start  decay,  and,  after  this  has  commenced,  putre- 
faction ensues. 

It  is  also  claimed  that  the  decay  of  organic  matter  is  not 
due  simply  to  oxidation,  but  to  the  action  of  organisms, 
ferments,  or  enzymes,  which  attack  the  organic  substances  and 
decompose  them  into  their  original  elements  or  into  simpler 
compounds. 

The  ordinary  rate  at  which  sedimentary  rocks  are  deposited 
is  too  slow  to  effect  the  inhumation  of  animal  substances  so 
that  they  will  be  excluded  from  the  air  and  preserved. 

But  few  animal  remains  are  found  incased  in  ice,  and  these 


THE   GENESIS    OF    PETROLEUM   AND   ASPHALTUM.  7 

are  not  buried  beneath  the  earth;  there  is  no  other  way  in 
which  they  can  be  preserved  by  cold. 

There  is  no  way  in  nature  that  animal  remains  can  be 
maintained  at  a  temperature  of  100°  C.  from  the  time  of  their 
death  until  changed  to  bitumen. 

Very  seldom  are  animal  remains  preserved  by  antiseptics  in 
nature,  and,  if  so  preserved,  their  aggregate  amount  is  small. 
All  the  ways  that  can  be  employed  to  preserve  animal  sub- 
stances are  destructive  to  animal  life.  The  presence  of  life 
and  the  conditions  and  way  necessary  for  the  preservation  of 
animal  substances  cannot  exist  in  the  same  place  at  the 
same  time. 

In  order  that  petroleum  oil  may  be  derived  from  animal 
remains,  it  is  first  necessary  that  such  remains  be  placed  and 
preserved  in  a  condition  for  such  change. 

In  the  present  age,  the  inevitable  end  of  animals  after  life  is 
to  furnish  nutriment  to  the  scavengers  of  the  earth  and  sea, 
or  their  decomposition  by  putrefaction. 

There  is  no  reason  why,  in  former  ages,  this  was  not  the 
ultimate  fate  of  animals. 

The  products  of  the  decomposition  of  nitrogenized  animal 
substances  are  as  follows:  The  oxygen  of  the  substance  unites 
with  the  carbon  to  form  carbonic  acid,  while  the  hydrogen 
divides  itself  between  the  nitrogen,  the  sulphur,  and  the 
phosphorus,  and  forms  ammonia  with  sulphuretted  and 
phosphoretted  hydrogen. 

The  surroundings  would  indicate  that  the  fossils  in  the 
petroliferous  formations  of  California  lived  and  died,  and  were 
embedded  in  the  same  manner  as  the  mollusca  of  the  present 
day;  in  fact,  a  large  number  of  the  fossils  in  these  formations 
are  the  prototypes  of  existing  mollusca,  and  must  have  lived 
and  died  in  the  same  manner.  There  is  nothing  showing 
that  after  death  the  mollusca  existing  at  the  present  day  are 
preserved  for  the  future  manufacture  of  petroleum.  This  is 
also  true  of  the  infusoria. 

The  fossil  animals  do  not  show  any  stage  of  transition 
between  animal  matter  and  petroleum  oil. 

Large  quantities  of  fossil  shells  exist  in  the  shales  and  sand- 
stones of  California;  these  are  usually  filled  with  silt,  or  the 
shells  have  been  changed  to  silica,  and  the  interior  filled  with 
silica,  or  molds  and  casts  exist,  the  carbonate  of  lime  having 


8  CALIPORNIA    STATE    MINING    BUREAU. 

been  leached  away.  They  only  contain  bitumen  when  the 
interspaces  and  cracks  in  the  adjoining  rocks  are  filled  with 
bitumen.  There  is  no  carbon  in  these  fossils,  except  in  some 
instances  the  carbonate  of  lime  constituting  their  shells.  There 
is  no  carbonaceous  matter  from  which  bitumens  could  be 
derived  by  any  known  process.  There  are  no  more  fossils  in 
the  rocks  which  are  impregnated  with  bitumen  than  in  those 
which  are  destitute  of  bitumen. 

Bitumens  are  found  in  the  unaltered  sedimentary  rocks  of 
California  sandstones,  shales,  limestones,  etc.  There  is  no 
bitumen  in  the  metamorphic  rocks.  The  only  substances 
originally  contained  in  these  rocks,  that  could  and  can  be  con- 
verted into  bitumen,  are  organic  vegetable  remains  in  the  form 
of  coal,  lignite,  and  carbonaceous  shales.  These  carbonaceous 
substances  are  not  changed  to  bituminous  unless  distilled  by 
heat. 

Most  all  of  the  known  beds  of  coal,  lignite,  and  carbonaceous 
shale  belong  to  the  cretaceous  or  tertiary  formation. 

If  bitumens  exist  in  them  at  all,  the  surrounding  and  accom- 
panying phenomena  show  that  these  accumulations  of  bitumen 
are  secondary. 

.  A  primary  deposit  of  petroleum  is  in  the  rocks  in  which  it 
was  formed. 

A  secondary  deposit  is  where  it  has  migrated  from  the  rocks 
in  which  it  was  formed  and  accumulated  in  other  rocks. 

If  petroleum  is  produced  by  destructive  distillation,  it  cannot 
remain  in  the  rocks  in  which  it  is  formed. 

The  petroleum  of  California  is  not  confined  to  any  particular 
geological  horizon  in  the  Coast  Range,  but  may  exist  in  any 
of  the  sedimentary  rocks  lying  above  the  altered  rocks;  there- 
fore, palaeontology  is  of  but  little  value  in  determining  its 
location. 

The  chief  guide  to  the  discovery  of  bituminous  accumula- 
tions is  the  character  of  the  rocks  constituting  the  formation, 
and  their  structure  and  position. 

There  is  no  evidence  tending  to  show  that  these  accumula- 
tions or  deposits  are  primary;  and,  if  secondary,  they  may 
occur  in  any  porous  or  seamed  sedimentary  strata  of  any  age 
lying  above  the  altered  rocks. 

The  age  of  a  formation  may  assist  in  the  discovery  of  pri- 
mary mineral  deposits;  but  migratory  fluids  and  gases  will 


^-... 

^ 


^^^^ 


THE    GENESIS    OF    PETROLEUM   AND   ASPHALTUM.        ^<^yl  9 

circulate  through  any  porous  or  seamed  strata,  and  accumulate 
in  such  places  as  are  rendered  suitable  through  structure  and 
position,  irrespective  of  the  age  of  the  rocks. 

The  accumulations  of  bitumens  in  the  domes  and  summits 
of  the  anticlines,  and  the  existence  of  tar  and  gas  springs, 
prove  that  they  were,  and  are  at  the  present  time,  migratory, 
and  that  the  principal  direction  of  their  migrations  was,  and 
is,  upwards. 

In  California,  the  upper  cretaceous  and  the  eocene,  miocene, 
pliocene,  and  quaternary  formations,  when  not  metamor- 
phosed or  otherwise  changed,  consist  of  soft  shales,  sandstones, 
conglomerates,  and  limestone.  The  large  majority  of  these 
rocks  are  soft  shales  and  sandstones.  The  rocks  of  one  age 
resemble  those  of  another. 

In  California,  the  miocene  seems  to  contain  the  largest 
amount  of  petroleum ;  this  is  owing  to  the  fact  that,  in  ascend- 
ing from  its  place  of  origin  below,  it  had  not  reached  the 
pliocene  in  the  same  quantity  as  it  did  in  the  miocene;  the 
pliocene,  being  the  farthest  away  from  the  place  of  its  origin 
and  the  eocene,  does  not  have  the  same  amount  of  exposures 
as  the  other  formations,  and,  when  visible,  the  formation  is 
so  broken,  and  tilted  to  such  high  angles,  that  the  oil  has 
escaped. 

The  fossil  shells  are  vastly  more  numerous  in  the  tertiary 
rocks  of  California  than  the  remains  of  all  other  kinds  of 
animals  put  together.  Mollusca,  similar  to  those  of  California, 
abound  to  an  extraordinary  degree  in  the  tertiary  in  other 
places  besides  California,  but  usually  they  contain  no 
petroleum. 

In  none  of  these  ages  are  animal  remains  found  in  a  state 
fit  for  the  future  manufacture  of  petroleum.  Neither  can  there 
be  found  any  substance  that  would  suggest  a  state  of  transition 
between  the  fauna  of  these  ages  and  bitumen. 

But  suppose,  for  argument's  sake,  that  it  is  admitted  that 
petroleum  oil  is  derived  from  animal  remains.  There  is  no 
reason  why  the  fauna  of  one  of  these  ages  should  not  be  the 
origin  of  petroleum  as  well  as  the  fauna  of  another  of  these 
ages.  Oil  which  can  be  claimed  as  being  indigenous  is  not 
found  in  the  quaternary. 

In  California  there  are  large  areas  of  fine  sand  containing 
many  fossil  shells  which  contain  no  bitumen;  if  they  had  at 


10  CALIFORNIA   STATE    MINING    BUREAU. 

any  time  contained  bitumen,  there  would  still  be  some  bitumen 
remaining  in  them,  as  there  are  many  shells  lying  in  such  a 
position  that  the  bitumen  could  not  escape  by  draining  from, 
or  being  floated  out  of  them.  If  the  petroleum  originated  in 
these  shells,  each  shell  would  contain  a  modicum  of  oil,  and 
would  not  be  completely  filled  with  petroleum  or  entirely 
destitute  of  the  same,  these  being  the  conditions  in  which  they 
are  usually  found. 

If  these  fossil  shells  are  full,  these  deposits  must  be  partly 
or  wholly  a  secondary  one,  as  no  mollusk  could  produce  a 
quantity  of  oil  equal  to  the  size  of  its  body;  and  if  they  were 
destitute  of  oil,  it  would  tend  to  prove  that  they  are  not  the 
source  of  oil. 

It  certainly  cannot  be  claimed  that  animal  remains  in 
anticlines  produce  oil,  while  similar  remains  in  the  synclines 
are  unproductive. 

The  presence  of  nitrogen  in  the  bitumen  does  not  prove  that 
petroleum  containing  nitrogen  is  of  animal  origin,  as  nearly 
all  plant  remains  contain  nitrogen  in  greater  or  less  quantity, 
and  yield  nitrogenous  compounds  by  distillation. 

How  can  the  different  kinds  of  bitumen  be  accounted  for  if 
they  are  derived  from  animal  remains?  Is  the  oil  that  originates 
from  one  species  of  mollusca  different  from  that  which  is 
derived  from  another? 

In  Russia,  the  petroleum  consists  principally  of  the  naph- 
tene  series;  in  Pennsylvania,  of  the  paraffine  series  and  a 
paraffine  base;  in  California,  of  the  define  series  with  an 
asphalt  base. 

Adjoining  fossil  shells,  when  bituminized,  contain  similar 
bitumens;  for  instance,  if  one  shell  is  found  inclosing  a 
bitumen  containing  six  per  cent  of  sulphur,  the  adjoining 
shells  all  contain  bitumen  containing  six  per  cent  of  sulphur. 
This  large  amount  of  sulphur  was  not  originally  present  in  the 
body  of  the  mollusca,  consequently  it  must  have  been  derived 
from  some  other  source,  and  if  derived  from  some  extraneous 
source,  the  percentage  of  sulphur  in  the  bitumen  in  each  shell 
would  not  have  been  so  constant — some  would  contain  more 
sulphur  than  the  other.  This  would  lead  to  the  belief  that 
the  bitumen  was  sulphurized  before  entering  the  shells,  and 
is,  therefore,  a  secondary  deposit. 


THE   GENESIS    OF    PETROLEUM    AND   ASPHALTUM.  11 

Then  there  are  varieties  of  asphaltites,  uinteite,  albertite^ 
grahamite,  and  elaterite. 

It  does  not  seem  possible  that  the  bodies  of  the  mollusca^ 
which  so  closely  resemble  each  other  in  composition,  should 
produce  so  many  dissimilar  bitumens. 

When  petroleum  is  found  in  fossil  shells,  it  is  also  found  in 
the  porous  or  seamed  strata  in  which  the  shells  are  embedded. 

The  character  of  the  bitumen  in  the  shells  is  the  same  as 
that  which  is  in  the  porous  strata,  excepting  that  it  is  some- 
times in  a  more  liquid  condition,  owing  to  the  fact  that  a 
greater  opportunity  is  offered  for  the  evaporation  of  the  bitumen 
in  porous  strata  than  in  closed  shells. 

Owing  to  the  buoyancy  of  the  bitumens  in  fresh  or  mineral 
water,  their  migrations  are  usually  upwards  until  checked  by 
impervious  strata,  or  until  they  have  reached  the  highest  point 
to  which  water  will  float  them,  or  until  they  reach  the  surface 
of  the  earth. 

Very  seldom  do  they  descend,  and  then  descent  only  occurs 
when  the  strata  to  which  they  have  ascended  are  uplifted  above 
permanent  water  by  orogenic  movements.  They  may  migrate 
for  a  thousand  feet,  and,  as  stated  above,  generally  upwards. 

In  the  Ojai  Valley  is  an  accumulation  of  asphalt,  lying  like 
a  huge  black  tear  upon  a  hillside,  which  has  slowly  issued  from 
the  small  springs  at  its  upper  end.  Scattered  throughout  the 
Coast  Range  are  similar  deposits. 

Distillation. — The  maximum  quantity  of  liquid  hydrocar- 
bons is  obtained  from  the  solids  by  a  process  of  distillation 
under  high  pressure  and  low  temperature,  combined  with  rapid 
condensation. 

Temperature  and  pressure  exercise  a  considerable  influence 
on  the  nature  of  the  products  of  distillation.  The  method  of 
cooling  also  exercises  great  influence  in  the  re-arranging  of  the 
molecules  and  upon  the  nature  of  the  product  of  distillation. 

Slow  cooling  or  quick  cooling  makes  no  difference  on  some 
substances,  but  the  difierence  between  slow  and  rapid  cooling 
has  a  marked  effect  on  others. 

If  we  reduce  the  heat  of  water  from  a  high  to  a  low  tem- 
perature, it  will  not  affect  the  constitution  of  the  water; 
whether  we  lower  the  temperature  slowly  or  quickly,  the  result 
will  be  the  same.     Water  that  is  slowly  cooled  from  the  boiling 


12  CALIFORNIA   STATE   MINING   BUREAU. 

point  down  to  the  freezing  point  will  have  the  same  properties 
as  water  that  is  rapidly  cooled  down  from  212°  to  32°  F.;  but 
that  does  not  hold  good  with  all  substances.  For  example,  if 
we  take  three  bars  of  steel  of  equal  dimensions  and  make  them 
all- red-hot;  then,  if  we  slowly  cool  one  bar  down  to  say  50°  in 
the  air,  and  if  we  cool  the  second  bar  by  slipping  it  slowly 
into  cold  water,  and  if  the  third  bar  be  suddenly  cooled  by 
plunging  it  into  cold  water,  the  time  of  cooling  these  three 
bars  of  steel  will  produce  a  different  effect  in  each  bar.  The 
bar  that  is  slowly  cooled  in  the  air  will  remain  comparatively 
soft  and  be  of  fibrous  texture,  malleable,  and  ductile,  capable 
of  being  bent  double  without  breaking.  The  second  bar  will 
be  harder  and  more  elastic,  and  can  only  be.  bent  a  small 
degree  without  breaking.  The  third  bar  will  be  very  hard  and 
brittle  and  cannot  be  bent,  and  if  struck  with  a  hammer  will 
fly  to  pieces,  the  fracture  showing  crystalline  structure.  Now, 
these  three  bars  were  simply  deprived  of  the  same  number  of 
degrees  of  heat.  They  were  reduced  from  an  equally  high 
degree  of  heat  to  an  equally  low  temperature,  but  we  find  that 
the  difference  in  time  occupied  in  cooling  makes  a  vast  differ- 
ence in  the  molecular  structure  and  properties  of  the  metal. 

These  facts  are  well  known  to  all  workers  in  metal;  but  it  is 
not  so  well  known  that  in  cooling  mixed  gases,  especially  the 
hydrocarbons,  from  a  high  to  a  low  temperature,  the  effect  on 
the  constitution  of  the  gases  varies  with  the  time  occupied  in 
cooling,  and  that  difference  between  quiescence  and  agitation 
during  cooling  has  different  effects  on  the  molecular  constitu- 
tion of  mixed  gases,  especially  with  mixed  hydrocarbons. 

Place  two  retorts,  of  the  kind  used  for  making  illuminating 
gas  from  coal,  in  one  oven,  so  that  they  will  get  equally  heated 
up  to  a  bright,  red  heat,  and  let  us  charge  each  retort  with  one 
hundred-weight  of  good  coal,  which  will  make  five  hundred 
feet  of  gas.  Now,  let  us  cool  the  gas  from  retort  number  one 
slowly  by  passing  the  gas  slowly  through  a  number  of  pipes 
placed  vertically  in  the  open  air,  in  the  manner  usually  done 
in  gas  works;  let  us  cool  the  gas  from  number  two  retort 
rapidly  by  passing  the  gas  through  a  multitubular  condenser 
surrounded  with  a  freezing  mixture,  and  we  will  find  the  result 
to  be  that  five  hundred  feet  of  permanent  gas  and  five  pounds 
of  tar  will  be  delivered  by  number  one  retort,  and  we  shall  get 
about  eight  hundred  feet  of  permanent  gas  and  thirteen  pounds 


THE  GENESIS  OF  PETROLEUM  AND  ASPHALTUM.       13 

of  tar  from  number  two  retort.  There  we  find  that  rapid  con- 
densation reduces  two  fifths  of  the  gas  to  a  liquid  state;  and 
if  we  w^ere  to  distill  under  high  pressure  and  low  temperature, 
we  should,  with  rapid  condensation  accompanied  with  agitation, 
reduce  nine  tenths  of  the  gas  to  a  liquid  state.  To  produce 
permanent  gas  from  coal,  we  should  distill  under  low  pressure 
and  high  temperature,  and  cool  the  vapors  rapidly  under 
agitation. 

When  gas  is  violently  agitated  during  the  cooling  process,  a 
greater  quantity  is  condensed  into  the  liquid  state  than  when 
kept  in  a  quiescent  state  during  the  cooling  process. 

When  gas,  much  cooled,  is  passed  through  a  coke  tower  down 
which  heavy  oil  is  trickling,  this  oil  will  absorb  the  light 
hydrocarbons  of  the  gas.  t 

The  boiling  points  of  the  hydrocarbons  of  petroleum  are 
altered  very  considerably  by  foreign,  or  even  by  the  traces  of 
foreign,  substances  being  present.  The  presence  of  difi'erent 
substances  during  distillation  has  an  influence  on  the 
distillate.  It  has  been  found  that,  when  a  mixture  of  chlorine 
with  hydric  chloric  is  passed  through  an  ordinary  charged 
gas  retort,  it  acts  as  a  hydrogenating  or  dissociating  agent, 
producing  a  tar  very  rich  in  benzol.  On  the  other  hand,  zinc 
chloride  in  the  presence  of  hydric  chloride  greatly  increases  the 
yield  of  heavy  hydrocarbides  from  coal,  and  can  convert  some 
of  the  lighter  constituents  of  the  tar  when  distilled  therewith 
into  heavy  ones. 

The  nature  of  the  product  also  depends  on  the  material  of 
the  retort.     A  rough  surface  will  facilitate  chemical  changes. 

By  repeated  distillations  solid  paraffine  can  be  gradually 
changed  into  liquid  kinds  of  paraffines  and  olefines. 

Mineral  tar,  by  repeated  distillation  in  the  presence  of 
superheated  steam,  will  be  converted  into  gas  if  the  united 
vapors  of  the  steam  and  tar  are  decomposed  by  heat  after  each 
distillation. 

Sulphur,  when  present  in  a  still  with  paraffine,  retards  its 
ebullition.  The  introduction  of  sulphur  into  a  paraffine 
boiling  at  140°-156°  C.  may  retard  its  boiling  point  as  far  as 
180°-200°  C,  according  as  it  may  exist  in  a  greater  or  less 
quantity.  In  consequence  of  the  presence  of  the  sulphur  in 
the  still  retarding  the  ebullition,  the  vapors  of  the  paraffine 
are  heated  to  a  point  far  above  their  boiling  points;  therefore, 


14 


CALIFORNIA    STATE   MINING   BUREAU. 


they  are  decomposed  to  hydrogen  and  carbon.  The  liberated 
hydrogen  combines  with  the  sulphur  vapors,  forming  sulphu- 
retted hydrogen. 

Shales  containing  y%  per  cent  of  sulphur  yield  scarcely  any 
paraffine  on  distillation. 


Yield  of 

Gas,  Oil,  Etc.,  feom  Shales  and 

Coals  at  High 

AND  Lo-^ 

N  Heat. 

Good  Shales. 

Boghead  Coal. 

Gas  ( 

30AL. 

fGas          

High. 

13.65 

3.65 

11.04 

.99 

2.82 

Low. 
2.54 
6.47 

17.65 

High. 

37.32 

2.43 

20.65 

.18 

.80 

Low. 

4.83 

3.23 

50.29 

High. 

20.49 

3.09 

17.08 

.29 

4.15 

Low. 
6.49 

Volatile . 

Am'onia  water. 

Tar  or  oil 

Sulphur 

Water  at  212°  E, 

Fixed  carbons. 

Sulphur 

Ash 

7.24 
26.45 

<3oke  — - 

32.15 

4.16 

1.05 

62.64 

26.66 
10.81 

62.53 

61.38 

9.01 

.06 
29.55 

58.35 
12.40 

29.25 

45.10 

45.00 

.34 

9.56 

40.18 
49.93 

9.89 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

What  is  known  under  the  general  name  of  petroleum 
includes  a  series  of  hydrocarbon  oils  varying  widely  in  physical 
properties.  Some  are  limpid  fluids  with  many  intermediate 
:grades;  others  are  found  viscid  and  tar-like. 

Hydrocarbons  generally  exist  in  three  different  conditions: 
first,  the  gaseous  condition,  wherein  the  equivalents  of  hydro- 
gen are  equal  to,  or  greater  than,  the  number  of  equivalents 
-of  carbon;  second,  in  the  liquid  state,  where  the  equivalents 
of  carbon  exceed  the  equivalents  of  hydrogen;  third,  in  the 
solid  state,  where  the  carbon  exceeds  the  hydrogen  in  still 
greater  ratio  than  in  the  liquid  state. 

Their  color  by  transmitted  light  ranges  from  a  light  yellow 
through  orange  and  red  to  a  reddish  brown,  so  dense  as  to  be 
translucent  only  in  thin  films;  while  by  reflected  light  it  passes 
from  a  light  dusky  color  to  a  dark  green  and  to  a  black.  They 
differ  as  markedly  in  odor,  and  also  in  other  properties,  some 
having  a  very  disagreeable  smell,  while  others  are  considered 
even  pleasant. 

There  is  a  wide  range  in  their  gravity.  The  greater  the 
quantity  of  carbon  in  proportion  to  the  hydrogen  any  one  of 
them  contains,  the  greater  is  its  specific  gravity,  and  the  higher 


THE    GENESIS    OF    PETROLEUM   AND    ASPHALTUM.  15 

its  boiling  point  and  density  of  vapor.  In  the  same  oil  field, 
in  the  same  series  of  strata,  and  in  the  same  stratum  there  are 
differences  of  composition. 

The  following  are  the  commercial  names  of  the  products  of 
distillation  of  crude  petroleum:  cymogene,  rigolene,  gasoline, 
naphtha,  benzine,  kerosene,  maltha,  and  paraffine.  There  is 
no  well-marked  division  line  between  any  of  the  above  named 
products,  but  they  gradually  merge  one  into  the  other. 

Their  division  is  simply  one  of  caprice.  These  hydrocarbons 
are  extremely  complex  and  different  in  composition.  The  pro- 
portion of  carbon  and  hydrogen  is  extremely  variable.  There 
seems  to  be  no  end  to  the  different  combinations  of  hydrogen 
and  carbon. 

The  great  diversity  in  the  physical  and  chemical  conditions 
of  the  bitumen  can  be  attributed:  first,  to  the  organic  remains 
from  which  it  was  distilled — different  kinds  of  terrestrial 
vegetation  and  marine  vegetation — by  natural  process  these 
organic  remains  may  have  been  changed  into  peat,  lignite,  or 
coal  before  distillation;  second,  to  the  degree  of  temperature  to 
which  organic  remains  are  subjected  during  distillation;  third, 
to  the  pressure  to  which  it  is  subjected  during  distillation; 
fourth,  to  the  time  consumed  in  effecting  distillation;  fifth,  to  the 
presence  of  different  substances  during  distillation — sulphur, 
lime,  water,  oxygen,  nitrogen,  etc.,  which  render  their  properties 
very  different;  sixth,  to  the  condensation  of  the  bitumen  after 
distillation,  whether  rapid  or  slow,  agitated  or  quiescent;  sev- 
enth, to  the  material  of  the  still;  eighth,  to  repeated  distillations; 
ninth,  to  evaporation;  tenth,  to  sulphuration,  oxygenation, 
etc.     Electricity  may  also  play  an  important  part. 

Maltha,  asphalt,  jew  pitch,  mineral  pitch,  and  brea  are 
hydrocarbons  which  contain  either  sulphur,  oxygen,  or  nitro- 
gen. They  may  contain  one  or  more  or  all  three  of  these 
elements  in  varying  proportions.  They  can  be  produced 
synthetically  by  sulphurizing,  oxidizing,  or  nitrogenizing 
petroleum  oils. 

Oxygen,  sulphur,  or  nitrogen,  when  chemically  united  with 
a  hydrocarbon,  such  as  some  of  the  petroleum  oils,  produces  a 
resin-like  substance,  to  wit:  asphaltum. 

One  of  the  solid  asphaltums,  when  taken  from  the  ground, 
is  brown,  owing  to  its  porous  condition,  caused  by  the  evapo- 
ration of  the  petrolene.     It  melts  at  245°  Fahr.     When  it  is 


16  CALIFORNIA    STATE   MINING    BUREAU. 

melted,  it  becomes  black  or  blackish  green.  Another  asphal- 
tum,  when  taken  from  the  ground,  is  black  in  color,  shaded 
with  brown,  or  red  and  dark  green  when  sulphur  is  present. 
When  purified  it  assumes  an  indigo-blue  reflection.  It  is 
opaque,  scentless,  tasteless,  and  fragile,  breaking  with  a  con- 
choidal  fracture,  which  has  a  glassy  brilliancy.  By  rubbing, 
it  acquires  a  resinous  electricity.  Its  specific  gravity  varies 
from  1.100  to  1.247.  At  ordinary  temperature  it  is  readily 
reduced  to  a  powder.  In  a  condition  of  extreme  subdivision 
it  takes  a  brownish  tinge.     It  melts  at  about  105°  to  108°  C. 

Immediately  above  its  melting  point  asphaltum  is  volatile, 
and,  if  the  temperature  is  carefully  raised,  it  disengages  in 
abundance  white  vapors  which  belong  to  oils,  which  become 
thicker  in  proportion  as  the  operation  is  prolonged  little  by 
little;  but  slowly  the  volume  of  vapors  diminishes,  gas  ceases 
to  form,  and  a  deposit  of  carbon,  slightly  bituminous,  is  reached, 
which  is  solid  and  has  the  appearance  and  often  the  hardness 
of  jet.  When  subjected  to  quick  distillation  in  passing  on 
towards  the  dark  red,  it  sets  free  at  the  same  time  a  mixture  of 
brown  oils,  sometimes  sulphuretted  hydrogen  and  sometimes 
ammonia,  while  the  retort  retains  about  one  third  of  its  weight 
of  loosely  compacted  carbon.  It  is  entirely  insoluble  in  water; 
it  gives  up  to  absolute  alcohol  a  small  quantity  of  a  yellow 
substance  which  exhales  the  odor,  and  has  the  appearance,  of 
resin.  Ether  extracts  from  it  a  brownish-black  substance 
called  petrolene.  The  portion  left  by  the  alcohol  and  the  ether 
is  asphaltene. 

The  yellow  substances,  petrolene  and  asphaltene,  do  not  exist 
in  asphaltum  in  defined  proportions.  Sometimes  the  petrolene 
will  represent  two  thirds  or  more  of  the  asphaltum.  On  the 
other  hand,  asphaltene  composes  almost  exclusively  other 
asphaltums.  The  properties  of  the  asphaltums  vary  according 
to  different  proportions  of  these  three  principles. 

Yellow  Resin. — Absolute  alcohol  dissolves  yellow  resin  with- 
out dissolving  petrolene  or  asphaltene;  it  is  also  readily  soluble 
in  the  solvents  of  petrolene  and  asphaltene.  It  has  the  appear- 
ance of  a  resin.  When  the  solution  in  alcohol  of  the  yellow 
resin-like  principle  is  treated  with  liquid  ammonia,  it  produces 
an  abundant  white  precipitate,  while  small  globules  of  petrolene 
spring  up  from  the  bosom  of  the  liquid  and  come  floating  in 
greenish-yellow  lentils  to  the  surface. 


THE   GENESIS   OF    PETROLEUM    AND    ASPHALTUM.  17 

Petrolene. — This  is  brownish  black  in  color  and  has  a  soft 
and  glutinous  consistency.  It  is  insoluble  in  absolute  alcohol. 
Ether,  benzine,  benzene,  acetone,  and  the  fat  oils  dissolve  it  and 
the  yellow  resin,  but  leave  the  asphaltene  intact. 

Petrolene  is  also  soluble  in  the  solvents  of  asphaltene.  The 
specific  gravity  of  petrolene  at  21°  C.  is  0.891.  It  burns  with  a 
very  sooty  flame.     It  has  but  very  little  taste. 

A  highly  concentrated  solution  of  caustic  soda  or  caustic 
potash,  when  hot,  dissolves  petrolene;  if  some  diluted  sulphuric 
acid  is  poured  into  the  liquid,  a  brown  gelatinous  substance  is 
precipitated. 

A  current  of  chlorine  precipitates  the  .  petrolene  from  its 
solution  in  benzine  or  in  turpentine  in  brown  and  viscous 
flakes.  These  precipitates  contain  chlorine,  and  do  not  give 
anything  further  to  alcohol  or  ether. 

Hydrochloric  acid  precipitates  petrolene  from  its  solution  in 
benzine  in  thick  flakes;  sulphuric  acid,  in  a  solid  and  viscous 
deposit,  which  is  transformed  in  time  into  a  brownish  red. 

In  making  the  experiment  with  sulphuric  acid,  the  acid  must 
be  carefully  and  slowly  added. 

If  asphaltum  be  kept  at  a  temperature  of  about  250°  C.  by 
means  of  an  oil  bath,  until  it  no  longer  loses  by  weight,  the 
petrolene  is  evaporated  from  the  asphaltene. 

Asphaltene. — Heavy  petroleum  oil,  carbolic  acid,  turpentine, 
chloroform,  and  bisulphide  of  carbon  dissolve  asphaltene  with- 
out residue.  It  burns  like  resin,  leaving  coke.  It  is  black, 
brilliant,  and  breaks  with  a  conchoidal  fracture.  In  the  fire  it 
only  becomes  soft  near  300°  C,  and  decomposes  before  com- 
pletely melting.  When  torrified  upon  a  platinum  plate,  it 
diffuses  an  odor  of  burned  fat,  afterwards  of  a  sharp  taste,  which 
reveals  an  acid.  It  is  solid,  hard,  and  fragile.  When  pulverized, 
it  presents  a  mass  of  purple  color,  oftener  of  a  brownish  red.  It 
develops,  by  friction,  resinous  electricity.  In  some  of  the 
asphaltums,  analysis  has  disclosed  a  large  proportion  of  oxygen; 
in  others,  a  large  proportion  of  sulphur.  A  current  of  chlorine 
precipitates  the  asphaltene  from  its  solution  in  petroleum  oils 
and  turpentine. 

Asphaltene  is  not  sensibly   affected   by   caustic  potash   or 
caustic  soda  in  a  concentrated  solution  in  water. 
2— Bl6 


18  california  state  mining  bureau. 

The  Formation  of  Asphaltum  by  the  Resinification  of 
Petroleum  Oils. — When  petroleum  oils  are  left  for  a  long  time 
in  the  presence  of  oxygen  gas,  or  the  atmosphere  which  contains 
oxygen,  and  in  the  light,  they  absorb  oxygen;  some  carbonic 
acid  is  set  free,  water  is  formed,  their  odor  becomes  weakened, 
and  they  likewise  become  viscous  while  they  assume  a  darker 
and  darker  color.  When  petroleum  oil  is  heated  in  a  current 
of  oxygen,  it  undergoes  a  quick  change  and  turns  into  petrolene. 

If  a  current  of  sulphuretted  hydrogen  is  conducted  into 
boiling  petroleum,  a  very  mobile  sulphurized  liquid  is  distilled, 
having  an  unbearable  odor  of  onions.  If  this  treatment 
is  repeated  with  the  new  compound,  a  second  portion  of 
the  sulphuretted  hydrogen  comes  to  reinforce  the  former,  and 
the  odor  of  the  liquid  becomes  that  of  garlic.  When  this 
sulphurized  oil  is  evaporated,  a  resin  is  formed. 

If  petroleum  oil  is  changed  by  the  compression  of  sulphuretted 
hydrogen,  and  then  the  sulphuretted  hydrogen  be  decomposed 
to  sulphur  and  water,  the  oil  will  be  sulphurized  and  resinified. 

If  petroleum  oil  is  distilled  in  the  presence  of  sulphur,  the 
oils  will  be  decomposed  and  sulphur  compounds  formed  in.  the 
shape  of  a  resin.  Petroleum  oil  treated  with  nitrous  gas 
absorbs  it  with  a  slight  development  of  heat;  the  petroleum 
becomes  thicker  and  is  partly  converted  into  resin. 

All  the  petroleum  upon  which  azotic  acid  is  caused  to  act, 
furnishes  yellow  resins. 

If  petroleum  is  boiled  in  a  concentrated  solution  of  nitrate  of 
potash  or  of  soda,  the  nitrate  converts  the  bitumen  into  resin, 
and  the  liquid  becomes  a  brownish  red. 

Polymerism  of  Asphaltum.— By  exposure  to  daylight,  as- 
phaltum polymerizes;  that  is,  it  acquires  a  higher  molecular 
weight,  retaining  the  same  atomic  proportions.  The  stronger 
the  daylight  the  more  rapid  polymerization  takes  place. 
When  polymerized,  its  molecule  consists  of  two  or  more  simple 
molecules  united  to  form  a  complex  molecule.  It  can  be 
changed  from  a  state  of  polymerization  to  its  original  or  simple 
state  by  heat. 

Polymerization  is  much  more  rapid  and  conspicuous  with 
asphaltene  than  with  petrolene;  the  part  of  asphaltum  soluble 
in  alcohol  does  not  polymerize. 

Polymerization  is  more   rapid   and  greater   in  asphaltum 


THE   GENESIS   OF   PETROLEUM   AND    ASPHALTUM.  19 

containing  sulphur  than  in  asphaltum  containing  oxygen. 
When  polymerized,  the  physical  properties  of  the  asphaltum 
are  changed;  it  has  a  greater  specific  gravity,  it  is  harder  and 
more  brittle;  but  the  most  marked  change  is  that  of  becoming 
insoluble,  or,  to  speak  more  exactly,  of  being  dissolved  with 
greater  difficulty  in  its  solvents  than  when  not  polymerized. 

Asphaltum,  on  account  of  this  photochemical  action,  is  used 
in  photography. 

If  a  moderately  concentrated  solution  of  asphaltum,  in 
spirits  of  turpentine  or  chloroform,  be  placed  in  a  transparent 
bottle  and  securely  corked,  and  then  exposed  for  some  time  to 
the  light  of  the  sun,  resinous  substances  separate  and  gradually 
appear,  which  dissolve  with  greater  difficulty  in  these  solvents. 
If  heated,  they  dissolve;  the  greater  portion  of  these  separated 
substances  adheres  firmly  to  the  sides  of  the  bottle;  a  smaller 
portion  remains  in  suspension  in  the  solution. 

Colored  resinous  substances  will  form  in  the  California 
petroleums  of  commerce,  if  exposed  to  light,  in  the  manner 
described  above.  *^ulter  Ij/^    2d        ,, 

Solutions  of  asphaltum,  which  are  to  be  employed  in  pho-  ^^^l6 

tography,  must  be  kept  in  the  dark. 

Asphaltum  is  employed  in  photography  in  the  following 
manner:  When  the  solution  of  asphaltum  with  turpentine  or 
chloroform  is  spread  over  a  plate,  and  left  in  a  dark  room 
until  it  becomes  nearly  dry,  which  will  require  a  few  days, 
and  the  plate  exposed  in  a  camera,  or  placed  under  an  object 
in  contact  with  it,  the  time  necessary  to  make  the  print  varies 
very  much,  and  can  only  be  ascertained  by  experiment.  When 
printed,  the  development  is  effected  by  quickly  flooding  with 
spirits  of  turpentine,  which  will  at  once  dissolve  the  asphaltum 
which  has  been  protected  from  light,  and  partly  dissolve  that 
portion  which  has  been  exposed  to  the  light.  As  soon  as  the 
subject  is  seen  to  be  fully  developed,  a  gentle  stream  of  water 
from  a  tap  is  allowed  to  flow  over  it  to  wash  off  the  turpentine. 
If  all  operations  have  been  conducted  rightly,  a  very  delicate 
and  perfect  picture  in  asphaltum  is  the  result. 

Anticlines,  synclines,  monoclines,  centroclines,  and  quaqua- 
versals,  and  also  faults,  exert  a  great  influence  in  the  accumu- 
lations of  gas,  petroleum  oil,  and  water.  Especially  is  this 
true  in  California,  where  the  dips  and  undulations  along  the 
strike  of  the  anticline  are  exposed  and  well  defined. 


20 


CALIFORNIA   STATE   MINING   BUREAU. 


Although  a  description  of  the  different  inclinations  and 
curvatures  of  strata  would  seem  elemental,  a  thorough  knowl- 
edge of  the  effect  of  these  inclinations  is  necessary  for  an 
understanding  of  the  laws  governing  the  accumulations  of 
bitumen  in  California.  In  the  Eastern  States  the  slopes  of  the 
domes  frequently  do  not  exceed  twenty  feet  to  a  mile,  whereas 
in  California  the  strata  stand  at  a  very  steep  angle  with  the 
horizon,  frequently  being  overturned. 


Fig.  1.— Plano-Section  Showing  Inclinations. 

When  a  group  of  strata  is  bent  into  a  curve  like  a  saddle, 
with  its  convexity  turned  towards  the  earth,  it  is  called  an 
anticlinal  curve.  Such  a  condition  of  strata  is  shown  in  Fig.  1 
above  the  word  "  anticline."  A  synclinal  curve  is  exactly  the 
opposite  of  an  anticlinal  curve.  When  the  strata  are  folded  or 
curved,  so  as  to  form  a  trough,  the  concave  side  of  which  is 
turned  from  the  earth,  this  is  called  a  synclinal  curve.  This  is 
shown  in  Fig.  1  above  the  word  ^'syncline."  In  both  anticlines 
and  synclines,  the  line  in  each  bed,  along  which  the  change  in 
the  direction  of  the  dip  takes  place,  is  called  the  anticlinal  or 
synclinal  axis  of  that  bed,  and  the  planes  containing  all  the 
axes  of  an  anticlinal  ridge,  or  a  synclinal  trough,  are  called 
axis  planes.  The  axis  plane  usually  approaches  verticality. 
Anticlines  and  synclines  frequently  nose  out,  or  coalesce. 

When  an  anticline  undulates  along  the  line  of  its  axis, 
dome-like  elevations  occur,  from  the  summits  of  which  the 
beds  dip  away  in  every  direction.  In  this  case  the  strata  are 
said  to  have  a  quaquaversal  dip.  An  anticline  is  an  elongated 
dome. 


THE   GENESIS   OF    PETROLEUM    AND   ASPHALTUM.  21 

A  quaquaversal,  or  dome,  is  a  nest,  usually  of  a  great 
number,  of  different  strata  composing  numerous  overlying, 
gigantic,  inverted  funnels,  the  strata  of  the  formation  forming 
the  sides  of  these  rock  funnels,  all  of  which  tend  to  guide  and 
convey  the  ascending  gas  and  oil  to  the  apex  of  the  dome. 

When  a  syncline  undulates  along  the  line  of  its  axis,  basin- 
shaped  depressions  occur,  towards  the  bottom  of  which  the 
beds  dip  from  all  sides.  This  is  called  a  centroclinal  dip.  A 
syncline  is  an  elongated  basin. 

A  fault,  or  dislocation,  is  a  fissure  or  crack  in  the  crust  of 
the  earth,  accompanied  by  the  elevation  of  the  mass  upon  one 
side  of  the  fault,  while  the  other  side  remains  stationary,  or 
sinks  down.  Anticlines  and  synclines  are  often  truncated  by 
faults,  and  may  be  so  faulted  as  to  form  the  segments  of  a 
sphere  or  cone.  If  an  oil-bearing  bed,  ascending  to  the  north, 
be  interrupted  by  an  east  and  west  fault,  the  further  ascent  of 
the  oil  northwards  will  be  arrested,  and  then  an  abundant 
supply  of  oil  may  be  obtained  by  boring  on  the  south  side  of 
the  fault;  while  for  a  considerable  distance  to  the  north,  water 
will  occupy  the  formation,  to  the  exclusion  of  the  oil.  This  is 
more  apt  to  be  the  case  where  the  throw  of  the  fault  is  sufiicient 
so  that  the  edges  of  the  porous  strata  are  covered  by  impervious 
strata.  Selvage  frequently  occupies  the  line  of  faults,  gener- 
ally caused  by  the  movement  of  the  two  sides  of  the  fault  on 
each  other,  which  have  ground  up  the  materials  of  the  rock, 
forming  a  sheet  of  matter  impervious  to  the  flow  of  oil  or  water, 
or  the  faults  may  be  filled  up  with  mineral  matter  of  various 
kinds,  which  are  also  impervious  to  oil  or  water. 

When  a  formation  contains  permanent  water,  the  accumula- 
tion of  petroleum  oil  will  be  found  near  the  upper  part  of  the 
dome,  as  is  shown  in  the  piano-section.  Fig.  1.  The  oil  floats 
on  the  surface  of  the  water,  and  if  natural  gas  is  present,  it 
will  be  found  above  the  oil.  These  three  substances  arrange 
themselves  according  to  their  specific  gravity,  the  lightest 
on  top. 

Fig.  2  (see  page  22)  is  a  view  of  an  anticline.  The  camera 
was  pointed  in  the  direction  of  its  strike.  The  black  line 
represents  the  plane  of  bedding,  which  was  once  horizontal, 
but  is  now  curved  in  the  form  of  an  arch. 

The  unaltered  rocks  of  California  cover  an  area  of  forty 
thousand  square  miles. 


22  CALIFORNIA    STATE    MINING    BUREAU. 

The  bitumens  are  found,  in  greater  or  less  quantities,  in  all 
of  the  unaltered  rocks  of  California  of  the  cretaceous  and 
tertiary  periods,  and  sometimes  in  the  quaternary  rocks,  in 
the  form  of  natural  gas,  petroleum  oil,  and  solid  and  liquid 
asphaltum.  The  difficulty  is  the  discovery  of  accumulations 
at  particular  places  large  enough  to  justify  developments. 

The  unaltered  rocks  consist  principally  of  alternating  beds 
of  shale,  sandstone,  and  conglomerate,  varying  in  thickness 


Fig.  2.— Mesa  Deposit,  Sisquoc,  Santa  Barbara  County. 

and  resting  upon  metamorphic  rock.  The  sandstones  and  con- 
glomerates act  as  reservoirs  for  the  accumulations  of  bitumen, 
and  the  shales  as  incasements  for  these  reservoirs.  Some  of 
these  sandstone  beds  are  more  than  three  hundred  feet  in 
thickness,  as  will  be  described  hereafter. 

Anticlines  exercise  great  influence  upon  the  accumulation  of 
natural  petroleum  oil  and  other  bitumens. 

The  main  anticlines  of  California  oil  regions  bear  north- 
westerly and  southeasterly.  The  summits  of  these  anticlines 
have  been  denuded,  exposing  metamorphic  rock.     Numerous 


THE    GENESIS   OP   PETROLEUM    AND   ASPHALTUM.  23 

smaller  anticlines  branch  in  all  directions  from  these  main 
anticlines,  and  generally  nose  out  in  the  valleys. 

Smaller  and  lower  anticlines  also  run  rudely  parallel  with 
the  main  anticlines. 

When  the  uplifts,  by  orogenic  movements,  have  been  great, 
the  apexes  of  the  anticlines  are  frequently  denuded,  the 
bitumens  either  being  washed  away  or,  as  more  often  hap- 
pens, drained  into  the  dips  of  the  anticlines. 

The  petroleum-bearing  strata  are  exposed  to  a  greater  geo- 
logical depth  in  the  outcrops  of  the  strata  of  the  main 
anticlines  that  show  a  metamorphic  core,  than  in  the  lower 
anticlines  that  are  but  slightly  denuded;  consequently,  there 
are  visible  many  seepages  of  oil  and  flows  of  gas  from  the 
outcrops  of  oil  strata  on  the  sides  of  the  main  anticlines,  while 
in  the  lower  anticlines  the  same  oil  strata  lie  far  below  the 
surface  of  the  earth.  In  the  valleys  in  which  bituminous 
strata  are  overlaid  by  quaternary  rocks,  the  bituminous 
deposits  may  exist  at  such  great  depths  that  they  cannot  be 
reached  by  drilling. 

In  the  northern  part  of  the  State  a  large  amount  of  tertiary 
rocks  have  been  washed  away ;  these  rocks  grow  thicker  and 
thicker  to  the  southward,  until  in  the  southern  part  of  the 
State  they  are  of  great  thickness.  The  unaltered  rocks  in  the 
northern  part  of  the  State  are  geographically  higher  and  more 
broken  than  in  the  southern  part.  Owing  to  these  diflerent 
conditions,  there  is  more  and  better  storage  room  for  the 
bitumens  in  the  southern  part  of  the  State  than  in  the 
northern. 

The  unaltered  rocks  of  the  Coast  Range  are  more  broken 
and  contorted,  and  have  a  much  larger  outcrop  than  those 
forming  the  foothills  of  the  Sierra  Nevada  on  the  east  side  of 
the  San  Joaquin  Valley.  Therefore,  there  are  more  visible 
evidences  of  bitumen  on  the  west  side  than  on  the  east  side  of 
valley. 

There  can  be  no  question  but  that  the  cretaceous  and 
tertiary  rocks,  which  are  the  oil-bearing  rocks,  of  California, 
underlie  the  quaternary  deposits  of  the  San  Joaquin  and  Sac- 
ramento valleys.  Gas  wells  exist  in  these  valleys ;  this  shows 
that  the  lighter  and  more  volatile  parts  of  the  petroleum  oil 
have  been  preserved;  consequently,  the  heavier  parts  of  the  oil 
exist. 


24  california  state  mining  bureau. 

Red  Shales  as  Connected  with  the  Genesis  of  Bitumen  in 
California. — Shales  were,  and  are,  deposited  in  still  and  salt 
water.  The  iron  contained  in  these  waters  and  organic 
remains,  both  animal  and  vegetable,  and  other  materials 
constituting  the  shales,  were  deposited  contemporaneously. 

If  the  iron  was  the  peroxide  of  iron,  ferric  oxide  (FcaOg), 
by  contact  with  organic  remains,  it  was  deoxidized  and 
reduced  to  a  protoxide,  ferrous  oxide  (FeO),  by  the  absorption 
of  one  equivalent  of  its  oxygen ;  when  the  peroxide  was 
reduced  to  a  protoxide,  carbonic  acid,  produced  by  the  decom- 
position of  organic  matter,  then  united  with  the  protoxide, 
forming  carbonate  of  iron  (FeCOa). 

The  carbonate  of  iron  imparts  a  bluish  or  greenish  color  to 
the  deposit. 

The  accumulation  of  iron,  in  the  presence  of  an  excess  of 
organic  matter,  retains  the  form  of  ferrous  carbonate.  In  all 
coal  measures,  of  all  periods,  whether  carboniferous,  Jurassic, 
cretaceous,  or  tertiary,  or  in  all  cases  where  there  is  organic 
matter  in  excess  in  a  state  of  change — in  all  strata,  whether 
older  or  newer,  in  which  there  is  organic  matter  in  excess  in  a 
state  of  change  (not  graphite) — the  iron  is  in  the  form  of 
carbonate  protoxide,  or  ferrous  carbonate  (FeCOg). 

Sulphide  of  iron,  ferric  sulphide  (FeSg),  is  subsequently 
formed  and  deposited  instead  of  carbonate  of  iron.  The 
sulphates  of  lime  (CaOSOg)  and  magnesia  (MgOSOg-f-^HO), 
and  other  sulphates  which  exist  in  sea  water,  when  subjected 
to  the  action  of  decaying  organic  matter,  out  of  contact  with 
air,  are  deoxidized  and  converted  into  solubles,  from  which 
sulphuretted  hydrogen  gas  is  set  free  by  the  carbonic  acid  gas 
produced  by  the  decomposition  of  organic  matter.  Sulphu- 
retted hydrogen  converts  the  soluble  compounds  of  iron  into 
sulphide  of  iron.     The  color  of  pyrites  is  brass  yellow. 

The  presence  of  protoxide  of  iron,  and  of  iron  pyrites,  in 
these  shale  beds,  arises  from  the  considerable  amount  of 
organic  substances  exercising  a  reducing  action.  The  water 
flowing  from  the  mountain  heights,  where  there  are  no  organic 
substances,  exercises  at  first  an  oxidizing  influence,  by  virtue 
of  which  the  rocks  over  which  it  flows  are  decomposed. 

The  suspended  substances  carried  down  by  these  rivers,  and 
the  detritus  swept  along  their  beds,  come,  after  a  time,  in 
contact  with  organic  substances,  by  means  of  which  the  per- 


THE   GENESIS   OF   PETROLEUM    AND   ASPHALTUM.  25 

oxidized  iron  compounds  are  again  reduced.  Consequently,  the 
iron  thus  carried  into  the  sea  is,  for  the  most  part,  in  the  state 
of  protoxide,  either  combined  with  silica  or  with  carbonic 
acid,  the  silicate  being  suspended,  and  the  carbonate  dis- 
solved in  the  water. 

When  unaltered  by  oxidation,  the  carbonate  of  iron,  with 
varying  amounts  of  lime,  clay,  or  sand,  is  dark  grayish-blue 
or  green,  or  even  white,  in  color. 

When  unaltered  by  oxidation,  the  sulphide  of  iron  is  brassy 
yellow  in  color. 

From  the  preceding  explanation,  it  is  safe  to  say  that,  at  the 
time  of  their  deposition,  the  carbonaceous  shales  were  not  red; 
and  as  long  as  they  are  not  submitted  to  oxidizing  influences, 
they  will  not  become  red. 

When  carbonate  of  iron  is  exposed  to  the  oxidation  of  the 
air,  it  forms  limonite  (hydrous  ferric  oxide),  which  is  usually 
of  a  brownish  yellow,  or  brownish  red  color.  These  iron  ores 
are  found  in  all  stages  of  transformation.  On  the  outcrop, 
they  are  limonite;  under  dense  cover,  carbonate.  While  going 
from  the  outcrop  inward,  the  limonite  constantly  decreases  in 
proportion  to  the  carbonate.  In  the  alteration  of  the  compact 
carbonate,  the  line  of  chemical  change  and  color  is  usually 
very  sharply  defined,  and  the  limonite  covering  can  often  be 
entirely  removed  from  the  inclosed  core  of  carbonate  by  a 
blow  with  a  hammer,  the  limonite  covering  preventing  the 
carbonate  core  from  being  oxidized  by  the  air.  In  shales 
charged  with  gray  carbonates  of  iron,  the  following  reaction 
takes  place  by  the  action  of  the  air:  the  carbonic  acid  is 
released,  and  part  of  its  oxygen  oxidizes  the  iron. 

Gray  shales  containing  finely  divided  pyrites,  or  bisulphide 
of  iron,  are  converted  by  heat  into  bright  red,  the  sulphur 
being  released,  leaving  the  shales  charged  with  red  oxide. 

The  color  of  burnt  ferruginous  shale  is  entirely  due  to  the 
amount  of  iron  present.  Gray  shales  containing  less  than  one 
per  cent,  or  one  and  one  half  per  cent  of  iron,  change  by  heat 
to  various  shades  of  cream  color,  or  buff;  while  those  contain- 
ing two  per  cent  to  ten  per  cent,  or  twelve  per  cent  of  iron, 
produce,  by  heat,  pink  and  bright  red  bodies.  The  depth  of 
the  color  depends  merely  on  the  amount  of  iron  present,  the 
buff  shades  gradating  into  the  deeper  shades  of  red. 

A  group  of  stratified  rocks  usually  consists  of  various  species, 


26  CALIFORNIA   STATE   MINING   BUREAU. 

arranged  in  alternating  beds,  a  series  of  beds  of  many  hundreds, 
or  even  thousands,  of  feet  in  thickness,  containing  strata  of 
shale,  limestone,  or  sandstone. 

Some  strata  are  seamed  or  porous,  and  easily  penetrated  by 
fluids,  serving  as  conduits  and  reservoirs  for  fluids.  Some 
strata  are  nearly  impervious  to  fluids,  while  others  are  practi- 
cally so,  frequently  serving  as  incasements  for  the  conduits  and 
reservoirs  formed  in,  and  by,  porous  and  seamed  strata. 

All  stratified  beds  have  been  originally  deposited  in  a 
horizontal  position,  or  approximately  so.  While  these  beds 
were  in  the  horizontality  of  their  deposition,  and  incased  by 
impervious  strata,  there  was  little  or  no  circulation  of  fluids 
within  their  porous  or  seamed  strata.  When  they  were  tilted 
and  inclined  to  the  horizon,  at  angles  varying  from  the  hori- 
zontal to  nearly  absolute  perpendicularity,  and  their  porous 
and  seamed  strata  exposed  to  the  entrance  of  fluids,  by  denuda- 
tion, fracture,  or  otherwise,  and  an  exit  for  the  fluids  was 
supplied,  or  produced,  at  a  lower  level  than  the  place  of  its 
entrance,  the  circulation  of  fluids  commenced,  slowly  at  first, 
gradually  increasing  as  the  inclination  and  exposure  of  the 
different  strata  became  greater.  The  course  of  the  circulating 
fluids  was  complex  and  anfractuous. 

Water,  supplied  by  the  rainfall  of  the  region,  enters  at  the 
outcrop  of  the  porous  and  seamed  strata.  If  the  porous  and 
seamed  strata  are  incased  in  impervious  strata,  the  greater  the 
depth  to  which  the  strata  extend  from  the  place  of  entrance 
of  the  water,  the  greater  the  pressure  will  become.  In  some 
instances  this  pressure  will  be  very  great,  forcing  the  water 
into  comparatively  impenetrable  rocks. 

The  water,  percolating  and  circulating  through  the  porous 
and  seamed  strata,  by  its  solvent  action,  accumulates  mineral 
ingredients.  These  waters,  saturated  with  minerals,  coming  in 
contact  with  other  minerals  existing  in  the  shales,  by  chemical 
reaction  produce  heat.  This  heat  contracts  and  fractures  the 
shales,  permitting  a  freer  circulation  of  water. 

This  chemical  heat  distills  petroleum  from  carbonaceous 
shales,  and  oxidizes  the  carbonate  and  sulphide  of  iron,  produc- 
ing the  red  colors  of  the  shales,  and  water  of  different  temper- 
atures, charged  with  mineral  ingredients,  will  frequently  rise, 
by  hydrostatic  pressure,  through  fissures  and  faults,  etc.,  to  the 


THE   GENESIS   OF   PETROLEUM    AND   ASPHALTUM.  27 

surface  of  the  earth,  forming  mineral  springs.     These  springs 
are  often  accompanied  by  bitumen. 

But  very  few  fossils  exist  in  these  red  pyrogenous  shales,  as 
they  have  been  obliterated  by  the  solvent  action  of  hot  water, 
or  by  the  chemicals  held  in  solution  by  the  circulating  waters; 
or,  if  the  molds  or  casts  of  their  external  forms  existed,  they 
have  disappeared  from  the  same  causes,  or  they  have  been 
crushed  and  distorted  beyond  recognition. 

Red  Shales  in  California. — Red  shales  in  California  are 
the  effects  of  chemical  heat.  Strata  which  have  been  more  or 
less  altered  by  the  action  of  heat  emanating  in  the  strata 
from  chemical  reaction,  consist  of  burnt  shale,  porcelain  jasper, 
earth  clinkers,  slag,  and  white  shale. 

Burnt  Shale. — Its  color  is  usually  red,  sometimes  gray,  yel- 
low, or  brown,  and  gradating  from  cream  color  to  brilliant 
red.  It  is  clay,  or  shale  burnt,  but  not  so  much  changed  as  to 
form  a  porcelaneous  mass. 

Porcelain  Jasper. — It  is  shale,  or  changed  into  a  kind  of 
porcelain  by  the  action  of  heat.  It  is  dark  red,  yellow,  or 
striped  yellow  and  red. 

Earth  Clinker  or  Slag. — This  is  a  shale,  converted  into 
a  kind  of  clinker  slag.  It  is  black  brownish  or  reddish,  and 
it  has  occasionally  a  tempered  steel  tarnish. 

Sometimes  it  shows  iridescent  colors.  It  is  vesicular,  usually 
amorphous,  but  occasionally  possessing  the  prismatic  form  of 
artificial  coke. 

White  Shale. — During  these  chemical  fires,  carbonic  acid, 
sulphuretted  hydrogen,  and  aqueous  vapors  are  formed;  these 
exhalations,  in  passing  through  the  shale,  bleach  and  decom- 
pose it.  The  silicates  are  decomposed  by  the  continuous  action 
of  aqueous  vapors,  at  212°  Fahr.,  sulphuretted  hydrogen,  air, 
and  the  alkalies,  magnesia  and  lime,  are  nearly  removed,  and 
metallic  oxides  are  carried  away.  The  vapors  convert  the 
shale  into  a  white  clay,  or  nearly  white,  when  a  small  quantity 
of  iron  still  remains.  By  the  removal  of  the  alkalies  (mag- 
nesia and  lime)  and  metallic  oxides,  the  quantity  of  alumina 
and  silica  increases.  The  absence  of  the  bases,  such  as  lime 
and  iron,  in  these  bleached  shales,  gives  growth  to  a  different 


28  CALIFORNIA   STATE    MINING   BUREAU. 

vegetation  from  that  which  grows  where  these  bases  exist.  This 
difference  in  vegetation  is  a  good  index  to  deposits  of  petroleum 
and  bitumen.  The  removal  of  these  substances  makes  the 
shale  incapable  of  sustaining  vegetable  life;  the  absence  of,  or 
scarcity  of,  vegetation  is  indicative  of  this  action.  Immense 
beds  of  these  white  and  altered  shales  frequently  occur  in  the 
vicinity  of  bituminous  deposits,  generally  running  in  the 
direction  of  the  anticlines. 

"Not  infrequently  the  marine  shales,  through  which  hot 
silicated  waters  have  percolated,  and  from  which  the  bases, 
such  as  lime,  magnesia,  iron,  etc.,  have  been  carried  away 
by  the  solvent  action  of  these  waters,  contain  diatoms  in  large 
numbers,  whereas  the  adjoining  shales,  which  have  not  been 
leached,  do  not  contain  diatoms  in  any  notable  quantities. 

Diatoms  abound  in  the  hot  springs  of  California  and  Yellow- 
stone Park.  In  the  hot  springs  of  the  Yellowstone  Park, 
deposits  of  this  kind  are  now  forming  over  many  square  miles, 
and  are  five  or  six  feet  thick. 

Why  should  they  not  originate  and  abound  in  percolating 
hot  silicated  saline  waters,  and  be  deposited  in  the  interspaces 
and  joints  of  the  shales  through  which  the  water  percolates  ? 

Isolated  bodies  of  diatomaceous  earth  in  California  would 
indicate  that  they  originated  and  were  deposited  from  springs. 

At  the  Buena  Vista  Oil  Springs,  in  Kern  County,  quaternary 
deposits  of  infusorial  earth  exist,  the  stratification  of  which  is 
horizontal;  it  has  either  been  denuded  from  the  leached  and 
adjoining  formation,  and  deposited  in  still  water,  or  else  it 
originated  in  quaternary  waters,  and  then  deposited;  probably 
the  latter  is  the  case,  as  these  strata  do  not  show  the  presence 
of  other  material  from  the  adjoining  formation. 

From  the  immense  amount  of  mineral  matter  which  has 
been  carried  away  by  the  solvent  action  of  water — thousands 
of  tons  of  fossil  shells,  silica,  magnesia,  iron,  etc. — and  the 
large  area  now  occupied  by  the  whitened  shales,  the  flow  of 
mineral  water,  at  some  former  time,  must  have  been  very 
copious  as  compared  to  the  flow  at  the  present  time. 

The  illustration  (Fig.  3)  shows  an  outcrop  of  red  shales  and 
porcelanite  near  Mount  Solomon,  Santa  Barbara  County. 

Phenomena  Attending  Red  Shales. — The  red  shales  are 
discovered  by  their  bright  colors,  by  the  heat  of  the  earth  in 


THE    GENESIS   OF    PETROLEUM    AND   ASPHALTUM. 


29 


their  vicinity,  and  sometimes  by  smoke.  Sulphurous  and  other 
vapors  frequently  occur.  These  vapors,  in  their  course  upward, 
are  condensed,  and  incrust  the  fissures  of  the  rocks,  and  even 
the  surface  of  the  ground. 

Mineral  springs,  hot  and   cold,  issue  from  the   ground  in 
their  vicinity.     The  earth  is  charged  with  salts  and  minerals 


Fig.  3.— Outcrop  of  Red  Shales  akd  Porcelanite. 

occasioned  by  the  percolation  and  evaporation  of  these  mineral 
waters.  Shales,  through  the  joints  of  which  these  mineral 
waters  have  flowed,  have  become  impregnated  with  salts,  and 
the  salts,  subsequent  to  the  flow,  have  become  vitrified  by 
heat. 

They  are  further  known  by  the  issuance  of  warm  or  cold 
natural   hydrocarbon   gas,  by  seepages  of    bitumen  in  their 


30.  CALIFORNIA   STATE   MINING   BUREAU. 

neighborhood,  by  fissures,  joints,  and  porous  rock  filled  with 
asphalt,  and  by  the  almost  total  absence  of  fossils  in  the  burnt 
shale  porcelanite  and  clinkers,  which  have  been  obliterated  by 
hot  water  and  heat.  Before  chemical  heat  commenced,  these 
shales  did  not  contain  over  two  per  cent  of  carbonaceous 
matter — not  sufiicient  for  them  to  be  set  on  fire  at  the  surface. 

Physical  Characteristics.— When  unburnt,  these  shales 
are  easily  split  along  their  lines  of  lamination,  but  when  burnt 
to  a  tile  red,  or  to  a  greater  degree,  their  fissility  is  partly 
destroyed.  When  unburnt,  their  lines  of  lamination  are 
plainly  visible;  but  when  burnt,  their  lines  of  lamination  are 
obscured  or  obliterated.  When  unburnt,  they  have  a  clayey -like 
smell  when  breathed  upon ;  but  this  physical  characteristic  is 
partly,  if  not  altogether,  lost  when  they  are  burnt.  When 
unburnt  and  suspended  so  as  to  freely  vibrate,  they'  have  a 
dull  sound  when  struck;  but  when  burnt,  they  become  resonant. 
In  this  characteristic  they  resemble  brick.  Chemical  fires 
destroy,  or  partly  destroy,  their  lines  of  lamination,  their 
fissility,  and  their  argillaceous  smell  when  breathed  upon,  but 
increase  their  resonance.  These  characteristics  do  not  occur 
when  these  shales  are  discolored  by  the  oxidation  of  the  iron 
naturally  contained  in  them,  through  the  agency  of  water 
without  heat.  Serpentine  cups  filled  with  a  pigment  made 
from  these  bright  shales  are  dug  from  the  graves  of  the 
aborigines. 

About  thirteen  miles  east  of  Santa  Barbara  City,  an  excava- 
tion was  made  on  the  blufi"  of  the  ocean  for  the  road-bed  of  the 
Southern  Pacific  Railroad,  and  the  gray  shale,  charged  with 
chemical  substances  and  carbonaceous  matter,  taken  from  the 
excavation,  was  thrown  over  the  blufi",  forming  a  conical -shaped 
pile,  composed  of  pieces  of  shale  containing  from  one  to  eight 
cubic  inches.  Water  could  easily  penetrate  the  broken  shale,  and 
air  could  easily  circulate  through  the  mass.  When  the  winter 
rains  fell  upon  this  pile,  chemical  action  commenced,  producing 
sufficient  heat  to  vitrify  and  weld  the  pieces  of  shale  together. 
A  large  part  of  this  shale  was  burned  to  a  red  porcelanite,  and 
the  remainder  was  colored  a  buff  shade,  gradating  into  the 
deeper  shades  of  red.  Above  the  railroad  track,  the  face  of  the 
shale  bluff  has  been  cut  off  to  the  angle  of  repose  by  the 
railroad  company.  This  smooth  surface  is  a  good  place  to 
observe  the  action  of  chemical  heat  and  attending  phenomena. 


THE    GENESIS   OF    PETROLEUM   AND    ASPHALTUM. 


31 


La  Patera  Mine. — La  Patera  Mine  lies  nine  miles  west  of 
the  City  of  Santa  Barbara.  Its  relation  with  a  lake  and  the 
ocean  is  shown  in  Fig.  4.  The  lake  contains  about  sixty  acres. 
Along  the  periphery  of  the  lake,  the  stratification  of  the  shale 
dips  towards  the  lake  at  an  angle  varying  from  30°  to  40°.  The 
composition  and  the  arrangement  of  the  component  parts  of  the 
soil  are  the  same  upon  the  island  as  upon  the  mainland.  The 
shale  must  have  existed  at  a  level  shown  by  the  dotted  lines  in 
Fig.  4,  and  subsided  after  the  deposition  of  the  soil,  otherwise 
the  soil  would  not  have  been  deposited  upon  the  island  in  a 
manner  similar  to  that  of  the  mainland.  This  subsidence  was 
probably  occasioned  by  the  contraction  of  the  underlying  shale, 


Fig.  4.— La.  Patera  Mine,  Santa  Barbara,  California. 

produced  by  chemical  heat.  Some  idea  of  the  contraction  of 
the  shale  by  burning  may  be  learned  from  the  contraction  of 
brick  through  burning.  Before  burning  and  when  in  a  dry 
condition,  a  brick  is  8  inches  long;  when  burned — not  vitrified — 
it  is  7J  inches  long,  and  when  vitrified  it  is  7|  inches  long. 

If  the  basin  of  the  lake  near  the  La  Patera  Mine  had  been 
formed  by  erosion  of  the  land  by  sea  or  surface  water,  the  shale 
would  have  been  squarely  cut  off  and  not  contorted  so  as  to 
dip  towards  the  lake.  In  the  excavation  at  the  mine  at  the 
depth  of  100  feet,  a  temperature  of  105°  Fahr.  is  generated  in  the 
shales  by  chemical  heat.  Circumjacent  to  the  lake  are  fissures 
filled  with  hard  asphalt,  through  which  comminuted  shale  and 
mineral  water  are  disseminated. 


32 


CALIFORNIA   STATE    MINING   BUREAU. 


Off  the  shore,  petroleum  rises  from  submarine  springs,  cover- 
ing a  large  surface  of  the  ocean  with  a  thin  film  of  iridescent 
oil,  the  odor  of  which  can  be  detected  at  a  long  distance. 
Ledges  of  hard  asphalt  exist  in  the  ocean,  below  high  tide, 
which  run  nearly  parallel  with  the  shore.  Surface  wells  show 
the  existence  of  water  highly  charged  with  mineral  substances, 
in  which  petroleum  is  discovered.  So  far,  no  potable  water 
has  been  found  near  this  mine. 

Six  miles  west  of  Santa  Barbara,  on  the  Calera  Rancho,  and 
on  the  ocean  shore,  an  area  of  twenty  acres  has  subsided  some 


Fig.  5.— Lake  Formed  by  Subsidence  of  Land. 

twenty-five  feet;  of  this  subsidence,  four  feet  occurred  in  five 
years.  This  subsidence  has  occurred  through  the  contraction 
of  the  shale.  The  surface  of  the  subsidence  is  rifted  and 
seamed,  and  from  these  rifts  and  seams  sulphurous  and  other 
vapors  ascend.  The  ground  is  hot.  The  bluff  is  composed  of 
burnt  shales,  showing  tints  from  a  cream  color  to  a  brilliant 
red.  Water  containing  salt  seeps  from  the  base  of  the  bluff. 
Shales  with  carbonaceous  material,  shales  saturated  with 
bitumen,  and  smoky-looking  shales  surround  the  hot  places. 


THE   GENESIS   OF   PETROLEUM   AND   ASPHALTUM.  33 

Near  the  hot  places,  heavy  petroleum  oils  ooze  through  the 
shales.  To  the  eastward  and  westward  heavy  and  thick 
petroleum  tars  ascend  through  the  cracks  and  seams  and  joints 
of  the  shale.  Some  of  the  seams  of  shales,  containing  a  small 
proportion  of  bitumen,  have  hardened  to  such  an  extent  that 
they  resemble  dark  flint,  and  will  cut  glass. 

Lyell  gives  the  following:  "  Captain  Mallett  quotes  Guinillar, 
as  stating  in  his  description  of  the  Orinoco,  that  about  seventy 
years  ago  a  spot  of  land  on  the  western  coast  of  Trinidad,  near 
half-way  between  the  capital  and  an  Indian  village,  sunk 
suddenly,  and  was  immediately  replaced  by  a  small  lake  of 
pitch,  to  the  great  terror  of  the  inhabitants."  A  similar 
subsidence  at  an  earlier  period  may  probably  have  given  rise 
to  the  great  Pitch  Lake  of  Trinidad,  the  cavity  having  become 
gradually  filled  with  asphalt.  There  are  a  number  of  places 
in  California  near  these  red  shales  from  which  natural  gas 
issues.  Some  are  hot,  showing  that  they  are  formed  at  a  high 
temperature. 

Fig.  5  is  a  view  of  a  small  lake  formed  by  the  subsidence  of 
the  land  near  Mount  Solomon,  in  Santa  Barbara  County. 

It  may  not  be  out  of  place  to  mention  in  this  connection  the 
occurrences  of  red  shale  in  other  parts  of  the  world  in  which 
bituminous  deposits  are  known  to  exist. 

Red  Shales  in  the  Island  of  Trinidad. — The  formation  of 
the  island  of  Trinidad  consists  of  clay,  loose  sands,  shales, 
limestones,  calcareous  sandstones,  indurated  clays,  porcelanites 
of  brilliant  red  colors,  with  pitch  deposits  and  lignite  here 
and  there. 

The  only  substances  containing  sufficient  carbon  and 
hydrogen  for  the  formation  of  asphalt,  and  likely  to  be  inclosed 
in  the  strata,  are  vegetable  remains.  They  are  particularly 
abundant  at  La  Brea,  where  most  of  the  asphaltic  beds  have 
been  originally  carbonaceous  and  lignitic  shales.  Mineral 
springs  abound  throughout  the  island.  In  a  series  of  loose  sands, 
clay,  and  shale,  lies  Pitch  Lake,  seemingly  occupying  a  depres- 
sion in  the  strata.  (See  Fig.  6,  page  34.)  To  the  southward  of 
the  lake  the  shore  is  made  up  of  bold  cliffs,  the  strata  of  which 
consist  of  indurated  clays.  They  also  present  thick  veins  of  por- 
celain jasper.  Strata  of  loosely  coherent  sandstone  also  abound, 
some  of  which  are  impregnated  with  bitumen.  Rounded 
3— Bl6 


34 


CALIFORNIA    STATE   MINING   BUREAU. 


pebbles  of  pitch  and  porcelain  jasper  form  a  beach  at  the  foot 
of  the  cliffs.  A  species  of  coke  is  occasionally  observed  along 
the  shore  with  a  porous  structure  and  the  prismatic  form  of  the 
artificial  product,  but,  of  course,  much  denser,  on  account  of  the 
large  proportion  of  earth.  Near  the  lake  is  a  red,  yellowish 
substance,  semi-baked,  evidencing  that  a  considerable  degree  of 
heat  attended  its  formation.  Part  of  the  impurities  in  the 
Trinidad  asphalt  consist  of  comminuted  red  clays  or  shales, 
with  some  sand. 

It  is  evidently  not  adventitious  at  the  surface,  but  must  have 
been  thoroughly  incorporated,  and  brought  up  from  the  depths 
with  the  bitumen,  judging  from  the  constant  amount,  dissem- 


FiG.  G— Pi 


<  E  AT  Trinidad,  W.  I— From  an  old  print. 


ination,  and  character  in  all  parts  of  the  deposit.  Water,  con- 
taining all  the  mineral  ingredients  of  strong  thermal  water,  is 
found  in  the  Trinidad  asphalt.  The  presence  of  borates,  iodides, 
and  so  man}^  forms  of  sulphur  compounds,  and  other  charac- 
teristics, show  that  the  water  must  be  of  the  same  origin  as 
that  of  many  thermal  springs.  This  water,  in  all  unaltered 
pitch,  shows  that  the  formation  of  the  pitch  and  water  must 
have  been  simultaneous,  and  cannot  be  considered  adven- 
titious. 

It  would  be  impossible  for  water,  in  any  adventitious  way, 
to  become  intimately  mixed  with  the  bitumen,  so  as  to  form, 
practically,  an  emulsion.  Near  the  center  of  the  lake  is  a 
body  of   pitch,  softer,  blacker,  and  newer  than   that  of  the 


THE   GENESIS   OF    PETROLEUM    AND    ASPHALTUM.  36 

remainder  of  the  lake.  Gas  constantly  issues  from  the  cracks 
in  the  bitumen.  These  phenomena  show  that  asphalt  is 
being  distilled  at  the  present  time.  The  porcelanite  and  red 
shales  must  have  been  formed  by  heat  created  in  the  strata 
themselves,  as  these  shales  are  burned  uniformly,  in  no  place 
showing  a  greater  degree  of  heat  than  in  another.  They  are, 
probably,  formed  in  the  same  manner  as  similar  rocks  in  Cali- 
fornia. The  depression  in  which  Pitch  Lake  lies,  was,  probably, 
made  by  the  subsidence  of  the  surface  of  the  earth,  caused  by 
the  heat  contracting  the  underlying  shale.  There  was  no 
focus  to  this  heat,  no  central  point.  If  there  was,  in  the 
material  next  to  the  central  point  the  evidences  of  heat  would 
be  great,  gradually  decreasing  as  you  went  from  the  focus;, 
this  is  not  shown.  To  illustrate,  bricks  of  very  different  qualities 
are  to  be  found  in  the  same  kiln,  for  as  the  fire  is  applied  below 
in  arches,  the  lower  bricks  in  their  immediate  vicinity  will  be 
burnt  to  great  hardness,  or,  perhaps,  vitrified;  those  in  the 
middle  will  be  well  burned;  and  those  on  the  top  will  be  too  little 
burned.  Even  then  the  bricks  the  farthest  from  the  fire  would 
not  have  been  burned  to  this  extent,  if  it  were  not  for  the 
numerous  flues  left  between  the  bricks  in  the  construction  of 
the  kiln.  The  intense  heat  of  a  furnace  is  confined  by  a  foot- 
wall  of  firebrick.  Three  feet  of  lava  will  confine  the  heat  of 
melted  rock  underneath.  From  the  uniform  burning  of  these 
shales,  the  heat  must  have  originated  in  the  shales  themselves. 
A  good,  clean  red  heat  is  required  for  the  burning  of  brick;  it 
is  fair  to  suppose  that  this  temperature  is  required  to  produce 
red  shales. 

Porcelanites  and  vesicular  clinkers  are  scattered  throughout 
these  red  shales;  they  are  not  centralized.  No  fumaroles 
connect  these  porcelanites  with  a  central  fire.  Moisture  was 
concerned,  as  is  evidenced  by  their  even  burning.  Moisture 
was  the  vehicle  of  heat,  as  the  burning  would  not  have  been 
so  uniform  in  its  effect  if  disseminated  by  conduction  or 
radiation.  The  parts  of  the  shale  burned  to  porcelain  resemble 
earthenware  and  stoneware;  to  burn  earthenware  and  stoneware, 
a  clean,  white  heat  is  required. 

Arborescent  forms,  of  huge  scale,  of  these  hydrothermal 
shales  extend  their  ramifications  throughout  the  earth  in  the 
vicinity  of  bituminous  deposits.  This  form  also  goes  to  show 
that  their  burning  was  accomplished  by  chemical  action,  with 


36  CALIFORNIA    STATE    MINING    BUREAU. 

the  presence  of  moisture,  and  not  from  radiation  or  conduction 
from  a  focalized  fire.  Nearly  all  readily  solvent  substances, 
and  all  volatile  substances,  have  been  removed  from  these  red 
shales,  or,  where  solvent  substances  now  exist  in  them,  they 
are  different  from  those  that  were  in  them  at  the  time  of  their 
formation.  The  noticeable  bright  red  colors  of  these  shales 
could  not  have  been  produced  by  the  oxidation  of  the  iron  in 
the  shales  by  water  alone;  heat  must  have  been  present  to 
produce  them.  This  heat  would  be  sufficient  to  distill  any 
carbonaceous  substance  contained  in  them. 

In  the  metamorphic  rocks  of  the  San  Rafael  range  of 
mountains  of  Santa  Barbara  County,  it  can  be  plainly  seen 
that  these  porcelanized  shales  were  converted  into  serpentine. 
All  gradations  from  shale  to  serpentine  can  be  found:  shales 
reddened  by  heat,  porcelaneous  masses  still  retaining  the 
structure  of  shales,  and  porcelain  partly  converted  into  serpen- 
tine. There  are  no  visible  signs  of  metamorphic  action  now 
in  operation  where  the  serpentine  is  exposed  to  view,  but  in 
the  tertiary  shales  and  sandstones  to  the  west,  especially  in 
the  hills  lying  north  and  south  of  the  Los  Alamos  Valley,  this 
metamorphic  action  is  going  on  at  the  present  time. 

These  red  shales  lie  above  and  precede  greater  metamorphism, 
such  as  is  exhibited  by  serpentine  and  quartzite,  and,  probably, 
metamorphic  granite.  This  can  be  seen  where  erosion  has  been 
great  enough  to  expose  the  contact  between  metamorphic  rock 
and  red  and  unaltered  shales.  When  burnt,  the  cracks  and 
seams  in  the  shale  are  large,  showing  the  extent  to  which  they 
have  contracted.  Near  the  surface,  the  red  shales  are  vesicu- 
lar, and  look  as  if  they  had  faulted.  These  red  shales  are  very 
much  distorted  and  contorted;  many  of  the  contortions  have  a 
radius  of  but  a  few  feet.  No  carbonaceous  matter  exists  in 
these  red  shales.  No  bituminous  substances  exist  in  these  red 
shales,  unless  they  have  entered  subsequent  to  their  burning. 
There  is  also  an  absence  of  sulphur.  Carbonaceous  and  bitu- 
minous substances,  and  sulphur,  are  disseminated  throughout 
the  strata  adjoining  the  red  shales. 

At  the  time  of  their  deposition  in  sea  water,  and  before 
any  alteration  had  taken  place,  the  red  shales  should  contain 
chloride  of  calcium,  carbonate  of  calcium,  carbonate  of  iron, 
carbonate  of  magnesia,  sulphate  of  calcium,  etc.,  vegetable 
matter  in  a  fine  state  of  subdivision,  and,  in  some  places,  large 


THE   GENESIS   OF   PETROLEUM    AND    ASPHALTUM.  37 


deposits  of  vegetable  matter;  this  organic  matter,  in  time, 
becoming  carbonaceous  shales  and  seams  of  coal.  When  these 
shales  are  heated  with  a  chemical  heat,  the  following  described 
vapors  and  gases  are  given  off:  sulphur  dioxide,  carbonic  acid, 
sulphuretted  hydrogen,  carburetted  hydrogen,  distilled  from 
the  carbonaceous  substances,  nitrogen  derived  from  the  same 
source,  etc.  These  vapors  are  forced  into  the  circumjacent 
formation,  which  is  highly  charged  with  mineral  matter  origi- 
nally present  in  the  shale,  and  which  had  been  deposited  from 
hot  water.  Chemical  actions  arise  when  these  vapors,  or  their 
condensations,  come  in  contact  with  the  minerals  existing  in 
the  shales,  causing  heat.  There  remain  in  the  shales,  after  the 
vapors  and  gases  are  eliminated  by  heat,  oxide  of  calcium, 
oxide  of  iron,  etc.  Mineral  waters  and  gases  coming  in  contact 
with  these  substances  produce  heat.  These  chemical  actions 
and  reactions  are  complex  and  numerous.  By  these  chemical 
actions  and  reactions,  distillations  and  condensations,  the 
alteration  of  the  shale  by  heat  becomes  progressive  and  cyclic. 
This  heat,  under  great  pressure,  and  through  subsidences  and 
orogenic  movements,  is  intensified.  Chemical  reactions  are 
augmented  through  pressure  and  hydrothermal  action.  The 
hydrocarbons  and  other  substances  are  distilled  and  condensed, 
dissociated  and  united,  a  multiplicity  of  times.  Mineral  springs, 
ranging  in  temperature  from  that  of  the  earth,  from  which  they 
issue,  to  the  boiling  point,  are  frequent  in  the  neighborhood  of 
these  burnt  shales.  They  contain,  in  notable  quantities,  sul- 
phate of  sodium,  magnesium,  and  calcium,  aluminum,  carbon- 
ate of  sodium,  calcium,  and  magnesium,  chloride  of  sodium, 
potassium,  and  calcium,  silica,  and,  in  excess,  carbonic  acid, 
sulphuretted  hydrogen,  carburetted  hydrogen,  and  traces 
of  arsenic,  sulphuric  acid,  and  iron.  Besides  the  visible 
phenomena,  the  warmth  of  these  springs  shows  that  this 
metamorphic  action  is  still  in  progress. 

Deposits  of  bitumen,  in  California,  are  found  in  sedimentary 
rocks  of  all  ages,  and  principally  in  three  different  ways: 
1.  In  superficial  detritus;  2.  In  veins;  3.  In  porous  or  seamed 
strata.  The  bitumen  may  be  of  any  consistency — gaseous, 
fluid,  viscous,  or  solid. 

Bitumen  often  occurs  in  superficial  detritus  or  alluvium. 
This  character  of  deposit  is  usually  the  overflow  of  tar  springs, 
into  which   the  detritus  from  the  surrounding   country  has 


CALIFORNIA    STATE   MINING   BUREAU. 


been  washed  or  blown,  and,  where  mineral  tar  is  sufficiently 
liquid,  it  has  percolated  into  the  underlying  earth.  The 
detritus,  when  saturated  with  mineral  tar,  most  always  has 
been  repeatedly  burned,  leaving  black,  vesicular  clinkers, 
which  are  frequently  refilled,  where  there  has  been  a  flow  of 
tar  after  the  fire. 

Cooking  utensils  of  the  Indians  are  found  in  the  vicinity  of 

these  tar  springs, 
showing  that  they 
were  used  for  pur- 
poses of  fuel.  After 
this  they  were  set  on 
fire  by  shepherds,  so 
that  the  fleeces  of 
their  sheep  would 
not  be  injured,  or 
lambs  suffocated  by 
going  into  the  sticky 
mass.  Where  the 
bituminized  detritus 
has  escaped  the  fires, 
and  exists  below  the 
clinkers,  it  contains 
about  five  per  cent 
of  brown  and  friable 
bitumen,  having  a 
specific  gravity  less 
than  that  of  water. 
It  consists  of  seventy 
per  cent  of  asphal- 
tene  and  thirty  per 
cent  of  petrolene. 
The  accompanying 
map  section  and  view  show  the  Buena  Vista  Oil  Spring,  at 
Asphalto,  Kern  County,  California.     (Fig.  7.) 

The  mineral  tar  reaches  the  surface  at  the  place  marked  "  tar 
spring."  At  the  place  marked  *Har  springs,"  a  number  of 
trenches  have  been  cut,  and  a  tank  erected,  so  as  to  intercept 
and  save  the  tar.  These  trenches  are  cut  in  clinkers  and 
comminuted  shale,  which  is  often  saturated  with  tar.  Thin 
layers  of  detritus,  impregnated  with  mineral  tar,  lying  nearly 


Fig.  7.— Buena  Vista  Oil  Spring,  Asphalto,  Kern 
County,  California. 


THE    GENESIS   OF   PETROLEUM    AND    ASPHALTUM.  39 

horizontal,  are  intercalated  with  thicker  layers  of  detritus,  which 
contain  no  bitumen.  These  beds  are  formed  by  flows  from  the 
tar  springs  and  deposition  of  detritus  denuded  from  the 
adjoining  hills.  Before  this  deposit  was  worked,  mineral  tar 
had  flowed  from  the  springs  over  the  surface  of  the  clinkers, 
until  it  had  reached  a  thickness  of  from  one  to  six  inches; 
it  had  evaporated  and  oxidized,  becoming  stiff.  It  was  of 
different  degrees  of  purity,  sometimes  absolutely  pure;  at  other 
times,  it  contained  as  high  as  eighty  per  cent  of  detritus.  In 
1891  and  1892  this  concreted  tar  was  being  mined  and  refined. 
At  the  present  time  there  are  but  a  few  tons,  which  are 
scattered  over  the  ground,  in  small  pieces.  It  has  been 
estimated  that,  in  recent  years,  these  springs  afforded  about 
one  hundred  and  sixty  barrels  annually.  There  are  a  large 
number  of  other  tar  springs  in  California,  nearly  all  of  which 
have  been  burned  in  the  manner  described  above. 

In  the  shaft  sunk  at  the  Hancock  deposit,  lying  northwest  of 
the  City  of  Los  Angeles,  in  the  center  of  what  appeared  to  be  an 
old  tar  spring,  on  the  surface  were  found  the  bones  of  domestic 
animals — horses,  cattle,  sheep,  etc.;  at  a  greater  depth  the 
bones  of  the  bear,  elk,  and  other  wild  animals;  and,  resting  on 
the  shale  beneath  the  bituminized  sand,  at  a  depth  of  about 
thirty  feet,  were  the  bones  of  the  Elephas  Americanus.  During 
the  latter  part  of  the  summer  season,  in  California,  the  natural 
grasses  dry  up,  but,  owing  to  the  slight  amount  of  water 
which  ascends  with  the  bitumen,  as  it  does  at  the  present  time, 
many  years  ago,  during  the  dry  season,  there  grew,  surrounding 
these  asphalt  springs,  green  and  succulent  herbage.  This 
herbage  was  the  bait  of  the  trap  which  tempted  these  herbiv- 
orous animals  to  their  death.  With  everything  else  dry,  these 
green  herbs  were  an  irresistible  temptation.  In  struggling  to 
get  to  them,  the  animals  became  mired  in  the  tar  lake  and 
suffocated,  their  bones  gradually  sinking  to  the  bottom. 

The  Elephas  Americanus  seemed  to  be  the  first  one  that  met 
this  fate,  as  his  bones  rest  upon  the  underlying  shale,  below 
the  remainder  of  the  fossils.  These  springs  must  be  very  old, 
as  it  is  many  years  since  the  American  elephant  fed  upon  the 
plains  adjacent  to  the  spring. 

Veins  of  asphaltum,  being  rents,  seams,  and  fissures  filled 
with  asphaltum,  occur,  usually  vertical,  or  not  far  from  vertical. 
An  innumerable   number   of   small   faults,   contortions,   and 


40  CALIFORNIA    STATE   MINING    BUREAU. 

breaks  occur  in  the  formation  in  which  these  veins  of  asphal- 
tum  exist.  These  veins  of  asphaltum  occur  in  the  vicinity  of 
red  shales,  or  shales  that  have  been  burned  and  contracted  by 
chemical  heat;  the  contraction  of  the  shales  opened,  and  open 
cracks  and  seams  in  the  adjoining  formation  permitted  the 
ascent  of  the  asphaltum.  These  cracks  and  seams  extend  to 
such  depths  as  to  reach  deposits  of  petroleum  oil. 

From  observations  made  at  Asphalto,  Mount  Solomon,  La 
Patera,  and  other  places,  it  would  appear  that  these  fissures 
and  rents  and  faults  are  filled  with  bitumen  in  the  following 
manner:  Heavy  petroleum  oil  at  various  depths  below  the 
surface  of  the  earth,  in  porous  or  seamed  strata,  is  urged 
upwards,  principally  by  rock  pressure.  The  subsidence  of  the 
formation  in  which  the  asphalt  veins  occur,  is  caused  by  the 
contraction  of  the  shales  by  heat.  In  consequence  of  the 
subsidence,  the  shales  and  sandstones  are  very  much  broken 
and  contorted.  Around  the  edges  of  these  subsidences  these 
veins  of  asphaltum  are  found. 

The  specific  gravity  of  the  asphaltum  is  too  great  for  it  to  be 
buoyed  up  by  water,  and  the  formation  in  which  the  veins 
exist  is  too  broken  for  gas  to  exert  a  pressure,  but  hydrostatic 
and  gas  pressure  do,  in  some  instances,  urge  the  bitumen 
upwards.  When  ascending  in  porous  or  seamed  strata,  the 
petroleum  oil  is  partly  evaporated,  the  evaporated  portion 
forming  gas,  which  reaches  the  surface  through  passages  which 
are  closed  to  the  viscous  oil.  The  oil  is  readily  oxidized  on 
account  of  its  divided  state,  and,  if  sulphuretted  hydrogen 
or  sulphur  dioxide  is  present,  the  oil  is  resinified,  forming 
asphaltum.  By  sulphuration,  oxidation,  and  evaporation  the 
petroleum  oil  is  finally  hardened.  When  nearing  the  surface 
it  is  indurated  to  such  an  extent  that  it  rarely  ever  shows 
itself.  Polymerization  of  the  bitumen  by  photochemical  action 
of  the  light  also  assists  in  the  induration  of  the  bitumen  when 
nearing  the  surface. 

Adjoining  the  selvage  of  the  veins,  when  near  the  surface  of 
the  earth,  the  asphaltum  is  brown  and  friable,  fully  two  thirds 
of  which  is  asphaltene.  In  the  interior  of  the  vein  it  is  black 
and  shining,  and,  when  cold,  breaking  with  a  conchoidal 
fracture,  fully  two  thirds  of  which  is  petrolene.  The  propor- 
tional amount  of  petrolene  and  asphaltene  existing  in  the 
asphaltum  is   very  variable.      When    at    a    sufficient  depth, 


THE   GENESIS    OF    PETROLEUM    AND   ASPHALTUM. 


41 


SO  as  to  be  removed  to  a  considerable  degree  from  atmos- 
pheric influences,  the  brown  margin  of  asphaltum  does  not 
exist.  As  a  general  rule,  the  farther  from  atmospheric  influ- 
ences, the  more  liquid  the  asphaltum  will  be.  Bivalvular 
shells,  filled  with  petroleum,  are  frequently  found  in  these 
asphalt  veins,  the  bitumen  on  the  shells  being  much  more 
liquid  than  the  surrounding  asphalt,  and  of  a  lighter  color. 
The  asphalt  veins  are  rudely  parallel  to  the  periphery  of  the  red 
shale  deposits,  and  exist  along  the  margin  of  the  subsidences, 


Fig. 


-Asphalt  Veins,  Santa  Maria,  California. 


the  seams  for  the  reception  of  the  asphalt  having  been  opened 
by  the  movement  of  the  formation  towards  the  contracting 
shales,  permitting  the  ascent  of  the  asphalt,  forced  up  by  rock 
pressure.  The  parallelism  of  the  veins  to  the  periphery  of 
the  burnt  shales  is  frequently  changed  by  the  varying  hardness 
of  difi'erent  strata,  or  by  orogenic  contortions. 

When  the  hanging  wall  consists  of  hard  and  close-grained 
strata,  the  bitumen  will  accumulate  below  the  same,  which,  on 
account  of  its  being  conformable  with  the  plane  of  bedding  of 
the  adjoining  strata,  gives  it  the  appearance  of  having  been 
deposited  at  the  same  time  as  the  other  strata.     When  these 


42  CALIFORNIA   STATE   MINING   BUREAU. 

shales  are  burning,  large  amounts  of  sulphur  vapors  are 
disengaged.  It  is  reasonable  to  believe  that  these  vapors 
sulphurized  the  bitumen  in  their  neighborhood,  forming 
asphaltum.  Mineral  waters,  containing  sulphuretted  hydrogen 
in  large  quantities,  usually  accompany  the  ascent  of  the 
asphaltum.  The  earth  adjoining  the  veins  is  usually  charged 
with  mineral  matter,  deposited  from  infiltrated  mineral  water. 
If  these  openings  and  sulphur  vapors  had  not  been  made  and 
generated,  through  the  contraction  and  burning  of  the  shales 
by  chemical  heat,  the  asphaltum  would  not  have  been  formed, 
nor  could  it  have  reached  the  surface  of  the  earth. 

'  The  physical  characteristics  of  the  asphaltum  filling  these 
veins  are  extremely  variable.  In  consistency,  it  gradates  from 
a  hard  rock  to  a  viscous  condition.  The  asphaltum  contains, 
intimately  mixed,  from  one  per  cent  to  seventy  per  cent  of 
impurities.  The  impurities  hardly  ever  exceed  seventy-five 
per  cent.  The  presence  of  more  than  seventy-five  per  cent 
of  impurities  makes  the  bitumen  so  stiff  that  it  cannot  be 
forced  through  the  cracks  and  seams.  In  the  vicinity  of  the 
injected  veins  there  are  beds  of  shales  containing  from  ten  per 
cent  to  fifteen  per  cent  of  bitumen,  but  existing  rock  pressure 
is  unable  to  move  them. 

The  impurity  in  some  of  these  asphalts  is  infusorial  earth, 
in  others,  sand,  while  in  others,  finely  ground  shales  and 
angular  fragments  of  shales  and  fossil  shells,  or  all  of  these 
impurities  may  be  present  in  the  same  deposit.  Shale 
preponderates  as  an  impurity;  in  fact,  the  impurities  are 
derived  from  the  rock  which  the  asphaltum  encountered  during 
its  ascent.  Most  of  the  time  the  impurities  are  very  fine  and 
light,  making  the  refining  of  the  asphalt,  by  any  known 
process,  difficult. 

The  thickness  of  these  veins  of  asphaltum  is  variable;  some- 
times they  are  twenty  feet  in  thickness,  decreasing  until  they 
become  the  thickness  of  a  knife  blade.  In  exploring  for 
asphalts,  these  small  seams  are  followed,  and  often  lead  to 
thicker  parts.  The  asphaltum  breaks  with  a  conchoidal 
fracture,  some  of  these  conchiform  pieces  being  ten  feet  in 
diameter.  The  viscous  asphaltum  cannot  enter  the  interstices 
or  pores  of  the  rocks  of  the  formation;  especially  is  this  true 
where  the  pores  or  interstices  of  the  rocks  are  filled  with  quarry 
water;  consequently,  when  it  is  urged  upward  and  forward  by 


THE   GENESIS   OF    PETROLEUM   AND    ASPHALTUM.  43 

rock,  hydrostatic,  or  gas  pressure,  it  exerts  a  pressure  in  all 
directions  (similar  in  action  to  a  hydraulic  press),  and  through 
this  pressure  pushes  the  rocks  asunder,  making  room  for  itself. 

The  pressure  required  is  not  great  when  the  shale  is  contracted 
on  one  or  both  sides,  the  asphaltum  being  constantly  alert  to 
take  advantage  of  any  movement  of  the  earth. 

Next  to  these  bituminous  veins,  the  formation  is  of  a  bluish 
color,  owing  to  the  presence  of  a  slight  amount  of  bitumen. 
These  veins  entered  the  formation  subsequent  to  its  subsidence, 
as  the  veins  are  not  faulted;  although  frequently  very  tortuous, 
they  are  continuous.  These  veins  sometimes  bisect  the  brown 
bituminized  sand,  showing  that  they  were  injected  subsequent 
to  the  filling  of  these  sands  with  bitumen,  and  even  after  they 
had  become  brown  and  indurated  through  long  exposure. 
These  veins  of  asphaltum  frequently  contain  fossil  shells  and 
shark's  teeth,  which  must  have  been  brought  up  from  lower 
strata,  as  no  similar  fossils  occur  in  the  adjoining  walls  of  the 
vein.  These  fossil  shells  are  filled  with  bitumen,  mixed  with 
the  silt  and  sand  that  entered  them  when  they  died. 

The  bitumen  in  the  shells  must  have  been  much  more  liquid 
when  it  entered  them  than  at  the  present  time.  At  the  present 
time  the  bitumen  is  too  stiff  to  enter  the  shells.  Sometimes 
the  bitumen  in  the  shells  is  much  softer  than  that  in  the  veins, 
and  sometimes  it  is  of  a  yellow  color.  Slickensides,  on  both 
sides  of  these  bituminous  veins,  show  that  the  material  has 
moved  upwards.  Fossil  shells,  embedded  in  the  hanging  wall 
of  these  veins,  have  plowed  grooves  in  the  asphaltum  as  it 
ascended.  At  the  Waldorf  Mine  a  groove  was  formed  in  this 
manner,  ten  feet  in  length. 

These  veins  of  asphaltum,  in  several  instances,  are  found 
injected  into  the  detritus  which  has  descended  from  the  adjoining 
hills.  Tunnels  and  shafts,  excavated  in  the  formation  con- 
taining these  veins,  have  been  partly  filled  with  the  ascending 
bitumen.  At  the  La  Patera  Mine,  in  sinking  upon  some 
asphaltum,  it  was  discovered  that  the  excavation  was  being 
made  in  an  old  shaft,  which,  outside  of  the  earth  that  had  fallen 
into  it,  was  filled  with  asphaltum.  At  a  depth  of  fifteen  feet, 
an  old-fashioned  pick  and  sledge-hammer  were  found,  which 
must  have  been  buried  for  a  long  number  of  years.  Inquiries 
were  made,  but  it  could  not  be  ascertained  who  sunk  the  shaft. 
At  the  La  Patera,  limpid  sea  water  is  inclosed  in  cavities  in 


44  CALIFORNIA    STATE   MINING    BUREAU. 

the  asphaltum.  its  limpidity  showing  that  sea  water  has  no 
effect  upon  the  asphaltum.  In  the  Santa  Barbara  Channel, 
below  high-water  mark,  near  the  La  Patera  Mine,  veins  of  this 
mineral  occur.  Owing  to  the  plastic  nature  of  this  character  of 
asphalt,  and  the  broken  condition  of  the  formation  in  which  it 
usually  occurs,  it  is  very  difficult  to  mine.  When  inclines, 
tunnels,  shafts,  and  other  excavations  are  made  in  asphalt,  or 
near  it,  they  are  hard  to  maintain,  as  the  asphaltum  lying 
above  or  near  the  excavations,  even  below  them,  commences  to 
move  through  rock  pressure,  so  that  the  excavations  are  soon 
destroyed. 

Deposits  near  excavations  give  evidence  of  their  existence 
by  the  earth  bulging  into  the  excavation.  Wedges,  picks,  and 
other  tools,  used  in  mining  the  asphaltum,  become  sharp, 
instead  of  dulling. 

When  mined  and  relieved  from  pressure,  occluded  gas  expands 
in  the  asphaltum,  making  it  very  vesicular. 

In  Fig.  9,  A  A  portrays  unaltered  shale,  greatly  distorted  by 
subsidence,  caused  by  the  contraction  of  the  red  shale,  D  D. 
B  B  B  B,  veins  of  asphaltum  squeezed  and  forced  up  by  rock 
pressure  exerted  by  the  shale  A  A,  owing  to  their  broken  and 
contorted  condition.  C  C,  shales  filled  with  condensed  hydro- 
carbonSj  which  were  vaporized  by  hydrothermal  heat  in  the  red 
shales. 

Near  or  adjoining  the  red  shales,  the  shales  are  filled  with 
liquid  asphaltum;  in  some  places  the  shales  and  the  liquid 
asphaltum  have  formed  a  mud,  which  is  forced  outwards  and 
upwards  by  the  weight  of  the  superincumbent  shale,  through 
cracks  and  seams,  to  the  surface  of  the  earth.  Farther  away 
from  the  periphery  of  the  red  shale,  the  shale  has  a  smoky 
appearance,  owing  to  the  condensation  of  different  vapors, 
generated  by  hydrothermal  heat  in  the  red  shales,  D  D. 
D  D,  red  shales  which  have  contracted  through  the  action  of 
hydrothermal  heat,  such  contraction  causing  subsidences  in 
the  overlying  shales,  A  A — such  subsidences  opening  fissures 
and  cracks,  B  B  B  B,  permitting  the  ascent  of  the  bituminous 
mud,  urged  upwards  by  rock  pressure,  and,  maybe,  by  gas  and 
hydrostatic  pressure.  Underlying  the  red  shales  is  serpentine, 
being  shales  metamorphosed  to  a  greater  extent  than  the  red 
shales.  Engraving  Fig.  9  on  the  following  page  gives  a  view  of 
a  formation  into  which  veins  of  asphaltum  have  been  injected. 


THE    GENESIS    OF    PETROLEUM    AND    ASPHALTUM. 


45 


Reservoirs  for  oil  and  aspbaltum  are  created  as  follows:  The 
porosity  of  limestone  is  created  by  chemical  action,  the 
changing  of  limestone  into  dolomite;  the  porosity  of  sandstone, 


Fig.  9.— Plano-Section  Showing  Asphalt  Veins, 

by  the  solvent  action  of  water  leaching  out  the  cementing 
material,  such  as  lime,  silica,  iron,  etc.;  the  capacity  of  shale 
for  holding  oil,  or  bitumen,  by  the  mechanical  bending  and 
cracking  of  the  strata,  the  cracks  afifording  storage  room. 


46  CALIFORNIA    STATE    MINING    BUREAU. 

Limestone. — The  Trenton  limestone  is  very  productive  under 
certain  circumstances.  In  its  normal  condition  it  is  a  compact 
rock,  and  then  it  contains  neither  gas  nor  oil;  but,  over  large 
areas,  limestone  has  been  dolomitized,  and  so  transformed  into 
a  porous  and  cavernous  rock,  in  which  the  gas  and  oil  are 
contained. 

The  dolomitization  of  the  Trenton  limestone  is  probably 
occasioned  by  the  removal  of  carbonate  of  lime  by  the  solvent 
action  of  water  charged  with  certain  minerals,  and  as  the 
Trenton  limestone  contains  originally  a  small  percentage  of 
magnesia,  it  gradually  becomes  dolomitic  in  character,  and,  on 
account  of  its  reduced  bulk  and  crystallization,  porous  and 
cavernous. 

When  water  has  taken  possession  of  shale  in  the  shape  of 
quarry  water,  or  the  shale  is  saturated  with  water,  it  is  nearly 
impossible  for  oil  to  eject  the  water  and  enter  the  shale;  the 
reverse  is  also  true,  for,  when  oil  has  taken  possession  of  the 
shale,  it  *  is  nearly  impossible  for  water  to  enter  the  shale. 
This  is  undoubtedly  owing  to  capillary  attraction  of  the  fluids 
in  the  shale.  When  the  surface  of  a  capillary  tube  is  greased, 
it  exerts  but  little  capillary  attraction  upon  water,  and  when 
a  capillary  tube  is  moistened,  it  exerts  but  little  capillary 
attraction  upon  oil.  Other  rocks  act  the  same  as  shale;  the 
finer  the  grain  of  the  rock  the  greater  the  capillary  attraction, 
and  the  more  difficult  it  will  be  for  oil  to  replace  water,  or  for 
water  to  replace  oil. 

Shale,  occupied  by  water,  makes  a  good  incasement  for  oil 
and  asphaltum. 

The  retention  of  petroleum  and  pissasphalt,  in  the  porous 
and  seamed  rocks,  cannot  be  effected  without  the  accumulations 
or  reservoirs  having  a  cover  or  impervious  incasement.  This 
impervious  incasement  usually  consists  of  unfractured  shale 
or  other  close-textured  rocks,  or  porous  and  fractured  rocks 
cemented  and  sealed  with  indurated  bitumen  or  other  minerals. 

When  the  outcrop  of  bituminized  sand  is  exposed  to  the 
atmosphere  for  a  long  time,  the  bitumen  contained  in  it  loses 
its  volatile  parts  by  evaporation  and  oxidation,  turns  brown, 
and  is  easily  pulverized  between  the  fingers.  The  sand  sepa- 
rates from  the  bitumen,  and  the  bitumen  is  easily  ground  to  an 
impalpable  powder.  This  brown  asphaltum  extends  to  but  a 
short  distance  below  the  surface  of  the  stratum.     Beneath  the 


THE    GENESIS   OF    PETROLEUM   AND   ASPHALTUM.  47 

brown  coating  of  bituminized  sand  the  deposits  receive  a 
coating  of  hard  asphaltum,  made  hard  by  evaporation  and 
oxidation.  The  condition  of  the  bitumen  in  the  seamed  and 
cracked  shale  resembles  that  which  is  in  the  sand.  This  con- 
creted surface  is  impervious  to  the  flow  of  pissasphalt  and 
petroleum  oil,  and  frequently  sufficiently  tight  as  to  inclose 
natural  gas.  In  fact,  all  porous  or  seamed  rocks,  when  the 
base  of  the  saturating  petroleum  is  asphaltum,  become  water 
and  petroleum  tight,  by  reason  of  the  petroleum  becoming 
concreted  by  oxidation  and  evaporation;  the  same  as  when  a 
tree  is  wounded  by  a  cut  or  puncture,  the  impissated  sap  soon 
closes  the  pores,  so  that  little  sap  escapes.  The  surface  of  the 
bituminized  sands  and  shales  is  hard,  increasing  in  fluidity  as 
the  bitumen  enters  the  deposit,  or  is  removed  from  atmospheric 
influences. 

In  some  deposits,  a  short  distance  from  the  surface  will  show 
a  petroleum  oil  of  10°  Baume,  decreasing  at  1,000  feet  to  32° 
Baume. 

If  rather  stiff  maltha  is  melted  and  poured  into  a  hole  in  a 
sheet  of  iron  one  sixteenth  of  an  inch  in  diameter,  so  that  it 
will  form  a  thickness  one  sixteenth  of  an  inch  on  each  side  of 
the  sheet,  the  sheet  being  one  sixteenth  of  an  inch  thick,  it 
cannot  be  removed  with  a  pressure  of  water  equal  to  fifty 
pounds  to  the  square  inch.  The  prodigious  pressure  necessary 
to  force  maltha  through  the  interspaces  of  sand,  or  irregular 
seams  of  shales,  for  a  distance  of  several  hundred  feet,  can 
hardly  be  imagined.  In  fact,  the  salvation  of  most  of  the 
accumulations  of  petroleum  oil  in  California  is  owing  to  this 
induration  of  petroleum  by  oxidation  and  evaporation. 

This  impervious  coating  also  protects  the  oil  reservoirs  from 
the  entrance  of  surface  water. 

The  petroleum  oil,  in  passing  through  the  sand  or  shale, 
collects  the  silt  and  carries  it  forward.  This,  also,  assists  in 
forming  a  cover,  filling  up  the  places  through  which  the  liquid 
hydrocarbons  attempt  to  escape. 

Under  great  pressure,  the  petroleum  oils  are  constantly 
alert  to  take  possession  of  any  space  created  by  the  uplifting, 
or  other  movements,  of  the  earth;  and  if  these  oils  are  con- 
creted into  asphaltum,  by  oxidation  and  evaporation,  they 
retain  possession.  The  oil  occupying  the  surface  of  the  water 
in  a  formation  has  an  advantageous  position  to  perform  this 


48  CALIFORNIA    STATE    MINING   BUREAU. 

work,  as  the  formation  is  more  fractured  in  these  parts  than  in 
the  synclines  and  the  dips  of  the  anticlines. 

The  cut  (Fig.  10)  shows  strata  of  bituminized  sand  on  a 
ridge  running  north  and  south,  between  the  Coja  Creek  and  a 
branch  of  the  Baldwin  Creek,  seven  miles  west  of  Santa  Cruz, 
California.  The  bituminized  sand  lies  nearly  horizontal,  and 
extends  from  canon  to  canon,  through  the  ridge.  The  dip  of 
the  shales  and  sandstones  of  the  surrounding  country  shows 
that  this  is  the  apex  of  a  large  dome  covering  an  area  of  some 
twelve  square  miles.  Overlying  these  strata  of  bituminized 
sand  is  a  close-textured  shale,  forty  feet  thick,  and  underlying 
the  same  is  a  porous  and  incoherent  sand. 


Fig.  10.— C.  S.  I.  Co.'s  Mine,  Santa  Cruz  County,  California. 

The  Coja  Creek,  lying  immediately  west  of  this  deposit,  is 
200  feet  deep,  and  must  have  taken  many  thousands  of  years 
to  form.  Redwood  trees,  proving  by  their  concentric  circles 
to  be  several  hundred  years  of  age,  are  growing  in  the  bottom 
of  the  creek.  The  impregnation  of  the  sand  with  bitumen 
must  have  occurred  before  the  gulch  on  either  side  of  the 
deposit  commenced  to  form  through  denudation,  otherwise  the 
liquid  bitumen  would  have  run  out  of  the  porous  sand.  From 
the  horizontality  of  the  surface  of  the  porous  sand  which 
underlies  the  bituminous  strata,  it  must  have  been  filled  with 
water,  forming  a  horizontal  plane,  upon  which  the  bitumen 
floated.  This,  also,  must  have  occurred  before  the  denudation 
of  the  gulch  on  either  side.  The  petroleum  must  have  been 
under  considerable  pressure,  as  it  has  thoroughly  saturated 
the  sand  between  the  porous  sand  and  the  overlying  shale, 


THE   GENESIS   OF    PETROLEUM    AND    ASPHALTUM.  49 

and,  where  porous  places  have  existed  in  the  shale,  petroleum 
has  been  forced  into  them. 

Notwithstanding  the  thousands  of  years  which  this  bitumin- 
ized  stratum  has  been  exposed  to  the  elements,  the  bitumen 
in  the  interior  parts  of  the  deposit  is  at  present  liquid,  its 
liquidity  being  preserved  by  the  concretion  of  the  bitumen  on 
the  top,  bottom,  and  sides  of  the  deposit,  stopping  evaporation, 
oxidation,  and  leakage.  These  strata  of  sand,  when  bitumin- 
ized,  contain  gold  in  considerable  quantity:  whereas,  in  those 
portions  which  are  not  bituminized,  but  little  gold  exists. 
It  would  seem  that  the  gold  in  the  bituminized  sand  was 
protected  from  the  solvent  action  of  mineral  water,  the 
presence  of  the  bitumen  in  the  sand  stopping  the  percolation 
of  mineral  water;  whereas,  in  the  sands  not  bituminized,  this 
percolation  is  permitted,  and  the  gold  is  dissolved  and  carried 
away.  But  further  examination  will  be  required  to  be  positive 
that  such  is  the  case. 

Sand  rock,  sand,  and  sandstone  are  composed  mainly  of 
rounded  or  broken  grains  of  quartz  of  varying  form,  color, 
and  fineness.  The  material  cementing  the  grains  is  either 
argillaceous,  bituminous,  silicious,  or  calcareous,  or  a  mixture 
of  any  of  these  four  substances.  Some  of  these  sands  contain 
cementing  material,  some  in  such  a  small  quantity  that  they 
are  friable.  When  found  beneath  the  earth's  surface,  it  is 
seldom  in  an  incoherent  state.  When  they  are  porous,  they 
are  occupied  by  either  natural  gas,  petroleum  oil,  or  water 
(generally  of  a  mineral  character),  or  both  of  these  fluids 
and  gas. 

The  buoyancy  of  the  oil  in  associated  water  is  the  force 
which  impels  the  oil  upwards.  The  oil  is  carried  so  far 
upwards  that  it  sometimes  escapes  at  the  surface  in  the  form 
of  tar  springs,  or  seepages,  and  is  lost,  or  it  accumulates  in 
porous  or  seamed  strata  beneath  the  surface  of  the  earth.  For 
the  reception  of  the  petroleum  oil  or  gas,  the  sandstone  strata 
are  at  first  made  porous  by  the  solvent  power  of  water,  which 
removes  the  calcareous  and  silicious  cementing  material. 

Frequently    these     bituminized    sands    are    jointed,    and, 

although  this  adhesive  and  plastic  material,  when  excavated 

and  thrown  into  a  pile,  will  stick  together  so  that  it  has  to 

be  again  mined,  it  will  separate  readily  at  these  joints  when 

4— Bl6 


60 


CALIFORNIA   STATE    MINING   BUREAU. 


being  taken  from  the  deposit.  The  joints  are  often  filled 
with  mineral  matter,  such  as  carbonate  of  lime,  deposited  by 
circulation  of  waters  subsequent  to  the  bituminization  of  the 
sands.     (Fig.  11.) 


Fig.  U.— Bituminized  Sand  Showing  Joints. 


Fro.  12.— Bituminized  Sand  Show- 
ing CONTOBTKD  JOINTS. 


These  joints  are  probably  partly 
due  to  pressure,  as  they  seem  to  have 
a  trend  which  appears  to  be  at  right 
angles  with  the  line  of  the  steepest 
inclination  upon  which  bituminous 
deposits  rest,  but  always  nearly  per- 
pendicular to  the  plane  of  bedding. 
Some  deposits,  when  jointed  in  this 
manner,  appear  like  a  row  of  books 
upon  a  shelf. 

Fig.  12  shows  bituminous  strata 
on  the  Sisquoc  River,  in  Santa  Bar- 


THE    GENESIS   OF    PETROLEUM    AND    ASPHALTUM.  51 

bara  County.  By  the  movement  of  the  formation,  the  joints, 
filled  with  lime,  have  been  distorted  so  as  to  nearly  form  the 
letter  '*S,"  showing  that  there  has  been  a  considerable  move- 
ment since  the  bituminization  and  jointing  of  the  sand. 

Thes  trata  are  often  faulted  a  few  inches  at  these  joints.  In 
the  folding  of  a  formation,  the  shales  will  be  contorted,  and 
the  bituminized  sand  faulted  at  its  joints.  The  bendings  of 
the  bituminized  sand  are  never  very  small  and  acute,  whereas 
in  shale  they  are  small  and  acute. 

This  makes  a  formation  often  appear  unconformable,  but  it 
is  the  nonconformity  made  by  bending  and  faulting,  and  not 
of  deposition. 

The  argillaceous  material  cannot  be  removed  like  the 
calcareous  and  silicious  cementing  matter;  consequently,  sands 
cemented  with  argillaceous  material  seldom  contain  bitumin- 
ous accumulations  to  any  great  extent.  When  the  calcareous 
and  silicious  cementing  material  is  removed  by  circulating 
water,  the  oil,  if  present,  occupies  the  sand.  This  leaching 
generally  occurs  along  the  line  of  faults  and  on  the  summits  of 
anticlines,  as  they  more  readily  offer  avenues  for  the  egress  of 
water,  but  may  occur  along  anticlinal  dips  and  in  synclines; 
in  fact,  in  any  place  where  the  intricate  subterranean  course 
of  percolating  water  reaches  the  sandstone.  When  the 
circulating  water  has  been  copious,  the  calcareous  and  silicious 
cementing  material  has  bepn  carried  away  to  the  surface  of 
the  earth,  sometimes  forming  deposits  of  sinter,  tufa,  limestone, 
or  dolomite.  When  the  flow  of  these  waters,  charged  with 
carbonate  of  lime  and  silica,  has  been  feeble,  and  the  sandstone 
has  again  been  cemented  and  made  impervious  to  water,  then 
the  flow  of  water  ceases,  or  finds  some  other  path  of  escape. 

Deposits  of  petroleum  oil,  resembling  pools,  occur  in  the 
sandstone  stratum  in  which  the  circumjacent  sandstone  is 
cemented  with  calcareous  and  silicious  material.  The  portion 
of  the  stratum  now  occupied  by  the  bitumen  was  formerly 
occupied  by  the  carbonate  of  lime  or  silica,  the  lime  or  silica 
having  been  removed  by  the  solvent  action  of  percolating  and 
circulating  waters.  If  the  gas  and  oil  are  ever  removed  from 
these  porous  strata,  they  will,  in  all  probability,  be  again 
cemented  by  lime  or  silica,  if  water  again  takes  possession  and 
its  flow  is  feeble. 


52  CALIFORNIA   STATE   MINING    BUREAU. 

Shale  is  laminated  clay,  more  or  less  indurated,  splitting 
into  thin  sheets  along  the  original  laminae  of  deposition.  In 
California,  the  majority  of  shales  are  quite  soft,  being  easily 
cut  with  a  knife. 

A  large  proportion  of  the  oil  obtained  in  California  is  taken 
from  the  cracks  and  recesses  in  shale.  The  strata  are  arranged 
around  the  axis  of  the  anticline  in  concentric  circles.  During 
distortion,  occasioned  by  the  uplifting  of  the  strata,  there  would 
be  an  elongation  of  these  concentric  strata.  If  they  consisted 
of  non-elastic  shale,  they  would  be  cracked  and  seamed  trans- 
versely to  the  seams  of  their  bedding.  This  would  occur  to  a 
greater  extent  in  the  strata  farthest  from  the  axis  of  the 
anticline.  If  there  was  a  great  weight  of  superincumbent 
earth,  the  cracks  and  seams  would  not  be  so  large  along  the 
planes  of  bedding  of  the  shale.  Being  more  acutely  bent,  the 
strata  on  the  steep  side  of  an  unsymmetrical  flexure  would  be 
more  broken  than  on  the  other  side. 

During  their  uplifting,  the  strata  on  the  slopes  the  farthest 
away  from  the  axis  of  the  anticline  would  move  slower  than 
those  nearer  the  axis;  consequently,  one  stratum  would  move 
upon  the  other,  grinding  the  shale  into  plastic  mud,  and  luting 
seams  and  cracks,  which  would  assist  in  forming  an  incasement 
of  water  and  oil.  This  grinding  movement  also  keeps  cracks 
and  seams  from  occurring  parallel  with  and  along  the  planes 
of  bedding  of  the  shale.  When  the  shales  are  bituminized 
in  their  cracks  and  seams,  one  tenth  of  the  bitumen  is  in  the 
seams  that  occur  parallel  with  the  planes  of  bedding,  and 
nine  tenths  in  the  cracks  and  seams  that  occur  transverse  to 
these  planes.  Where  the  shales,  the  cracks  and  seams  of  which 
are  filled  with  bitumen,  which  resist  the  action  of  denudation 
better  than  the  shales  that  do  not  contain  it,  are  side  by  side, 
the  latter  are  worn  away  more  largely  than  the  former,  and  a 
valley  results,  owing  to  denudation  acting  unequally.  Many 
blutis,  and  prominent  peaks  and  ridges,  owe  their  existence  and 
stability  to  the  bitumen  in  the  cracks  and  seams  of  their 
shales. 

When  water  takes  possession  of  shale,  the  capillary  attraction 
ofiers  so  great  a  resistance  that  oil,  even  under  enormous 
pressure,  is  incapable  of  forcing  an  entrance  and  ejecting  the 
water.  When  oil  is  in  possession  of  the  shale,  the  same 
resistance  is  ofiered  to  the  entrance  of  water.     Shale  saturated 


THE   GENESIS   OF   PETROLEUM    AND    ASPHALTUM.  53 

with  water  is  a  far  better  covering  for  petroleum  than  dry 
shale.  Where  the  distortion  of  the  strata  has  been  acute,  the 
multiplicity  of  these  cracks  and  seams  makes  the  storing 
capacity  of  these  fractured  shales  very  large — in  fact,  many 
will  be  equal  in  this  respect  to  porous  sands.  For  reasons  stated 
heretofore,  the  cracks  and  seams  will  be  wider  on  the  summits 
of  anticlines  than  on  their  slopes  or  in  synclines.  Owing  to 
the  broken  condition  of  the  shale,  the  petroleum  has  ascended 
from  strata  to  strata,  and  not  for  any  great  distance  through 
any  particular  stratum  or  strata,  until  the  concretion  of  the 
bitumen,  by  exposure  to  atmospheric  actions,  assisted  by 
silicious  waters,  sealed  strata  from  each  other. 

Silica  and  Lime. — The  hot  waters  created  by  chemical  heat, 
held  in  solution  large  quantities  of  silica.  When  the  hot 
silicious  water  approached  the  surface  of  the  earth,  it  was 
cooled;  the  cooler  the  water  became,  the  less  capable  it  was  to 
hold  in  solution  this  large  amount  of  silica.  Cooling  of  the 
water  eliminated  the  silica,  which  was  deposited  in  the 
interstices  of  the  shales,  increasing  their  solidity  and  impervi- 
ousness.  There  may  also  be  an  interchange  between  the  silica 
dissolved  in  the  water  and  certain  constituents  in  the  sandstone 
and  shale — for  instance,  carbonate  of  lime — the  silica,  having 
a  greater  degree  of  hardness  than  the  substance  removed, 
would  be  deposited.  This  silicification  is  a  very  frequent 
phenomenon  in  these  rocks. 

If  the  silicious  water  circulated  through  particular  strata, 
the  silica  eliminated  by  the  cooling  of  the  silicious  water,  owing 
to  its  superior  gravity,  sank  to  the  bottom  of  the  strata  and 
cemented  the  same.  Strata  adjoining  the  hot,  silicious  water 
may  be  cooler  than  those  in  which  the  silicious  water  circulates; 
in  that  case  the  cooler  strata  act  as  condensers.  This  action 
created  the  strata  known  as  "shells";  the  shells  often  occur  on 
the  top  and  bottom  of  the  sands,  and  throughout  the  shales. 
This  silicification,  together  with  the  concreting  of  the  bitumen, 
creates  impervious  strata,  which  are  capable  of  holding  petro- 
leum oil  and  natural  gas.  These  silicifications,  when  formed  in 
'  strata  in  which  bitumen  occurs,  are  colored  black.  Their 
color  is  destroyed  by  burning,  proving  that  it  is  owing  to 
organic  material. 

Silica,  in  a  very  fine  condition,  is  frequently  attracted  to 


54  CALIFORNIA    STATE   MINING   BUREAU. 

some  organic  or  inorganic  nucleus  which  has  grown  in  suc- 
cessive layers  or  bands,  often  of  different  colors.  In  a  similar 
manner  the  small  silicious  particles,  separated  from  hot, 
silicious  solutions,  are  attracted  by  the  incasements  of  porous, 
or  partly  porous,  and  seamed  strata. 

Lime  is  controlled  usually  by  the  same  conditions  and 
laws  as  silica.  Large  masses  of  shale  and  sandstones  have 
been  calcified  and  salicified  near  the  bituminous  deposits  in 
California. 

Deposits  of  bitumen  and  petroleum  oil  are  controlled  by  the 
line  of  permanent  water.  Below  the  level  of  the  ocean,  all 
cracks,  seams,  fissures,  and  interspaces  are  permanently  filled 
with  water.  Above  the  level  of  the  ocean,  and  below  the  beds 
of  streams,  the  supply  of  water  in  these  spaces  is  fairly-perma- 
nent. Above  the  beds  of  streams  the  supply  of  water  is 
dependent  upon  the  rainfall,  and  the  degree  of  freedom  with 
which  it  leaves  the  formation. 

Pervious  and  impervious  strata  modify  the  above  conditions. 
Permanent  water  may  be  replaced  or  occupied  by  a  deposit  or 
column  of  bitumen,  petroleum  oil,  or  natural  gas.  When  the 
underlying  water,  which  supports  the  oil,  is  released  by  the 
uplifting  of  a  formation  above  the  permanent  water  by  erogenic 
movements,  the  water  leaves  the  formation,  and  the  oil  drains 
into  the  voids  formerly  occupied  by  the  water,  and,  possibly, 
reaches  the  surface  by  the  same  avenues  taken  by  the  water, 
and  is  lost  or  resinified  to  asphaltum.  Frequently  the  porous 
strata  accumulations  of  bitumen  have  resulted  through  the 
drainage  of  oil  from  a  higher  and  large  area  of  porous  rock 
into  a  lower  porous  stratum. 

The  bituminized  sands  on  the  mesa  deposit,  on  the  Sisquoc 
Rancho  (Fig.  13),  show  the  drainage  action.  They  are  drained 
into  a  centrocline,  the  sides  of  the  centrocline  afterwards 
having  been  carried  away  by  denundation;  the  water  which 
buoyed  up  the  oil  escaped,  and  the  oil  slowly  sought  the  bottom 
of  the  centrocline.  The  sands  forming  the  uppermost  edge  of 
the  centrocline  have,  to  a  great  extent,  lost  their  bitumen ;  as 
soon  as  the  bitumen  leaves  the  sand,  it  falls  into  an  incoherent 
mass,  and  is  rapidly  washed  away  by  rains.  The  existing 
bitumen,  in  consequence  of  the  long  distance  traveled,  has 
become  viscous,  principally  through  oxidation  and  evaporation. 

This  drainage  is  still  slowly  progressing,  as  in  hot  weather 


THE   GENESIS   OP   PETROLEUM   AND   ASPHALTUM. 


55 


balls  of  nearly  pure  bitumen 
form  on  the  surface  of  the 
sands  in  the  lower  part  of  the 
deposit. 

South  of  Asphalto,  in  Kern 
County,  the  bitumen  has 
reached  the  bottom  of  the 
syncline  by  drainage,  and  is 
now  gradually  descending 
through  the  syncline,  as 
through  a  ditch.  Although 
this  occurred  ages  ago,  this 
drainage  is  still  in  process. 

What  evidence  is  there  that 
water  circulates  and  circulat- 
ed through  these  formations  ?  B 
The    presence    of    calcareous  i 
tufa   at   the   outcrops  of   the  ^ 
strata;   the  presence  of  bitu-  ^ 
men  in  the  cracks  and  seams  2 
of  the  shales,  and  in  the  inter 
spaces  of  the  sands  floated  up  ^ 
by  associated  waters — if  the 
bitumen  was  forced  up  exclu-  | 
sively  by   gas,  it  would   not  | 
have  been  so  evenly  and  gen-  | 
erally  disseminated  through- 
out   the    shales    and    sands; 
springs  of  water  accompanied 
by  natural  gas  and  oil,  issuing 
from   the    outcrop   of    strata 
which  dip  towards  the  source 
of  the  water,  and  the  absence 
of  these  springs  from  the  out- 
crop of  strata  which  dip  away 
from  the  source  of  the  water; 
the  seams  of  hard  shale,  called 
"shells,"  silicated  by  infiltrat- 
ing silicious  waters;  nothing 
but  molds  and  casts  of  fossil 
shells,  the  carbonate  of  lime 


5ft'  CALIFORNIA   STATE   MINING   BUREAU. 

having  been  removed  in  solution  in  water.  Near  the  outcrops 
of  these  strata,  in  the  creek  and  river  beds,  the  sands  and 
gravels  are  cemented  together  with  carbonate  of  lime,  forming 
conglomerates. 

What  is  the  efi'ect  on  deposits  and  accumulations  of  bitumen 
by  circulating  waters,  fresh  and  mineral  ?  Petroleum  oil,  when 
exposed  for  a  long  time  to  water  containing  sulphuretted 
hydrogen,  is  resinified  by  being  sulphurized;  especially  is  this 
true  where  the  sulphur  is  liberated  by  decrease  of  pressure,  or  by 
the  oxidation  of  the  hydrogen.  The  sulphurizing  of  petroleum 
oils  by  sulphuretted  hydrogen  is  a  chemical  combination,  but,, 
if  only  a  mechanical  combination,  it  is  so  intimate  as  to 
resemble  a  chemical  combination. 

Petroleum  oil  will  be  oxidized  when  exposed  for  a  long  time 
to  water  containing  oxygen,  or  atmospheric  air.  Oxidation 
converts  the  oil  into  petrolene,  and  greatly  increases  its  gravity. 
As  slight  quantities  of  petroleum  oil  are  dissolved  in  fresh 
water,  the  lighter  parts  are  dissolved;  consequently,  the  effect 
of  circulating  fresh  water  is  to  carry  away  the  lighter  parts  of 
the  oil,  leaving  the  heavier  parts  behind.  Water  saturated 
with  salts  has  but  little  e£fect  on  petroleum  oil.  Sometimes 
the  salts,  through  the  agency  of  water,  are  mechanically  and 
intimately  mixed  with  the  bitumen,  so  as  to  render  their 
separation  difficult. 

Besides  these  chemical  effects  of  water  on  the  bitumen,  water 
exerts  the  following  described  hydrostatic  and  hydraulic  effects : 
In  cases  where  strata  are  rendered  leaky  by  denudation,  and 
water  is  ascending  to  the  surface  through  the  same,  the 
petroleum  oil  is  floated  out  on  the  surface  of  the  water  and  lost. 
Meteoric  water,  which  falls  on  higher  ground,  penetrates  the 
earth,  sometimes  to  great  depths,  through  inclined  and  porous 
strata,  or  through  fissures,  cracks,  seams,  and  joints  of  rocks; 
and,  after  flowing  a  distance,  sometimes  the  distance  being  very 
great,  it  must  ascend  through  permeable  strata  to  the  surface, 
or,  hidden,  flnd  its  subterraneous  way  to  the  sea.  The  course 
of  water  flowing  underground  is  not  strictly  analogous  to  that 
of  a  river  on  the  surface,  there  being,  in  one  case,  a  constant 
descent  from  a  higher  to  a  lower  level,  from  the  source  of  the 
stream  to  the  sea;  whereas,  in  the  other,  the  water  may  at  one 
time  sink  below  the  level  of  the  ocean,  and  afterwards  rise  high 
above  it,  by  hydrostatic  pressure,  due  to  the  superior  level  at 


THE    GENESIS   OF    PETROLEUM   AND    ASPHALTUM. 

which  the  ram-water  was  re- 
ceived, and  the  incasement  of 
permeable  strata  by  impervious 
strata. 

It  must   be   borne   in  mind 
that   the   circulation  of   water 
through  the  rocks  can  be  ex- 
tremely slow.     On   account  of 
the    broken    condition   of    the 
rock  on  the  anticlines,  caused  by  the 
acute  curvature  of  the  anticlinal  arch, 
and  its  greater  exposure  to  denuding 
agents,  far  greater  quantities  of  rock 
have  yielded  to  erosion  than  in  the 
synclines,  where  the  rocks  have  been 
hardened    by    lateral    pressure    and 
cemented   by  infiltration  of  minera 
waters.     This  broken  condition  of  the 
rocks  of  the  anticlines  permits  water 
to  enter  them  more  freely  than  the 
synclines  or   the  slopes  of  the   anti- 
clines, and  also  permits  more  readily 
the  escape  of  petroleum  oil  and  nat- 
ural gas.     The  accumulation  of  petro- 
leum oil  must  have  commenced 
when  these  rocks  were  but  slight- 
ly undulated.     The  former  and       4/ 
ancient  features  and  state  of  a 
formation  should  be  taken  into 
consideration,  as  well   as  those 
existing  at  the  present  time,  in 
the  examination  of  an  oil   field. 
If  there  is  no  opposing  force  or 
intervening  obstacle,  gas,  petro- 
leum oil,  and   water   distribute 
themselves  in  porous  or  seamed  strata 
in  accordance  with  the  difference  of 
their  gravity.     The  gas  lies  above  the 
petroleum  oil,  and  the  oil  floats  upon 
the  water.     It  must   be  remembered 
that,  under  ordinary  pressure,  oil  and 


57 


5/ 


68  CALIFORNIA    STATE   MINING    BUREAU. 

water  do  not  mix,  and  that  the  gravity  of  petroleum  oil  is  less 
than  that  of  water,  but  for  which  little  would  have  been  seen 
on  the  face  of  the  earth.  If  petroleum  oil  is  introduced  into 
the  bottom  of  a  vessel  filled  with  water,  it  will  rise  to  the  top 
of  the  water;  and  if  water  is  placed  on  the  surface  of  the  oil, 
it  will  sink  to  the  bottom  of  the  oil. 

The  pressure  of  water  is  exerted  below  the  petroleum  oil, 
and  the  pressure  of  natural  gas  above.  Porous  strata,  incased 
in  nearly  impervious  strata,  must  be  considered  as  conduits 
for  the  fluids,  petroleum  oil  and  water.  When  petroleum 
oil  and  water  flow  in  the  same  direction,  the  porous  and 
seamed  strata  are  liable  to  be  barren  of  oil.  Where  the  oil 
and  water  flow  in  opposite  directions,  the  porous  or  seamed 
strata  are  liable  to  be  fruitful  with  oil. 

Many  years  ago,  before  the  denudation  occurred,  these  strata 
were  incased  in  an  impervious  cover;  the  right-hand  dip  of  the 
anticline  was  towards  the  mountains;  meteoric  water,  falling  on 
the  mountains,  entered  the  porous  strata  at  A  (Fig.  14,  page  57), 
and  finally  flowed  up  the  right-hand  dip  of  the  anticline,  B, 
as  shown  by  the  arrows,  being  impelled  forward  by  hydro- 
static pressure  in  the  higher  levels  of  the  mountains;  and  the 
associated  oil  which  entered  these  strata,  by  its  inferior  gravity 
when  compared  with  water,  flowed  in  the  same  direction  as 
the  water;  therefore,  this  dip  of  the  anticline  is  barren  of 
bitumen.  In  the  left-hand  dip  of  the  anticline,  B,  the  water 
flowed  downward,  impelled  by  gravity,  and,  probably,  hydro- 
static pressure,  seeking  an  exit  as  springs  in  the  valleys,  or, 
unseen,  found  its  way  to  the  sea;  the  oil,  by  its  inferior  gravity, 
was  buoyed  up  by  the  water,  or  ascended  in  a  contrary  way  to 
the  flow  of  the  water;  consequently,  the  pores  and  seams  in 
this  dip  are  filled  with  bitumen.  These  same  conditions  exist 
in  the  Zaca  anticline,  Las  Pozitas  anticline,  lying  west  of 
Santa  Barbara,  and  at  Summerland,  and  many  other  places. 

The  following  is  an  exception  to  the  accumulation  of  oil  in 
the  dip  remote  from  the  source  of  circulating  water:  Petro- 
leum oil  is  nearly  always  accompanied  by  natural  gas.  If 
the  porous  or  seamed  strata,  serving  for  conduits  for  water 
or  oil,  have  vertical  curves  or  summits,  and  such  summits 
are  sufficiently  tight  to  hold  the  gas,  in  time  the  gas  will 
accumulate  in  such  summits  and  occupy  a  considerable  part 
of  the  sectional  area,  and  it  will  continue  to  accumulate  until 


THE   GENESIS   OF   PETROLEUM   AND    ASPHALTUIki?^;^        69 

the  velocity  of  the  water  or  oil  is  sufficient  to  carry  the  gas 
forward,  and  down  the  incline.  If  the  pressure  never  reaches 
such  a  point  as  to  effect  the  removal  of  the  gas,  the  flow  of  the 
water  or  oil  will  be  more  or  less  obstructed;  and,  finally,  if 
the  gas  is  not  removed,  or  does  not  escape,  the  flow  of  the  water 
or  oil  ceases.  In  this  case,  oil  will  be  found  in  the  dip  of  the 
anticline  which  is  towards  the  head,  from  which  the  water 
emanates. 

Fig.  15   shows   alternating   beds   of  different   sands,  all  of 
which  are  bituminized. 


Fig.  15.— Altebnating  Beds  of  Different  Sandstones. 

Strata  C  C  C  are  formed  of  coarse  quartz  sand,  containing 
round  pebbles  of  hard  rocks,  such  as  quartz.  They  do  not 
contain  many  fossils. 

Strata  B  B  B  are  formed  of  fine,  muddy  sand,  containing 
lenticular  pebbles  of  shale.  These  pebbles  have  been  silicated, 
forming  chert,  but  their  surfaces  still  retain  the  appearance  of 
shale,  and  they  have  the  lamination  of  shale. 

This  silicification  must  have  occurred  before  these  sands  were 
bituminized.     This  silicification  was,  probably,  effected  by  the 


60  CALIFORNIA    STATE   MINING   BUREAU. 

infiltration  of  hot  silicious  water.  The  creation  of  this  water 
was,  probably,  through  the  agency  of  metamorphism,  which 
preceded  the  distillation  of  petroleum  from  carbonaceous 
matter  by  the  heat  of  metamorphism. 

In  the  figure,  A  represents  fine  shale  with  few  fossil  shells; 
in  places  it  contains  fossil  fish-bones.  The  cracks  and  joints 
at  right  angles  with  the  planes  of  bedding  are  frequently  filled 
with  bitumen. 

No  cracks  at  right  angles  with  the  plane  of  bedding  could 
have  existed  in  these  shales  until  they  were  contorted;  there- 
fore, these  cracks  were  bituminized  after  the  folding  of  the 
formation  had  commenced.  Neither  could  bitumen  have 
ascended  through  these  shales  before  they  were  cracked  or 
jointed,  for  when  these  fine  shales  contain  quarry  water,  they 
are  impervious  to  oil. 

These  different  strata,  B  B  B  and  C  C  C,  are  conformable,  and 
do  not  pass  into  one  another  by  gradation;  the  lines  between 
them  are  clearly  marked.  The  muddy,  fine  sand  does  not 
weather  as  rapidly  as  the  coarse  sands;  consequently,  their 
faces  of  exposure  are  nearer  verticality  than  those  of  the  coarse 
sand. 

The  different  strata  must  have  been  derived  from  two  forma- 
tions, one  being  composed  of  altered  rocks,  and  the  other  of 
unaltered  rocks,  and  the  changes  in  the  derivation  of  the 
sediments  composing  this  formation,  from  the  altered  to  the 
unaltered  rocks,  were  quickly  made,  either  by  a  change  in 
ocean  currents  or  by  the  sudden  uplifting  of  the  land. 

These  strata  of  sand,  described  above,  are  situated  on  the 
Tinaquaic  Rancho,  in  Santa  Barbara  County.  The  character 
of  the  bituminized  sands  near  Santa  Cruz  is  very  difierent. 
They  contain  few  round  pebbles  of  hard  rock,  and  no  lenticular 
pebbles  of  shale.  They  are  clean  quartz  sands,  of  varying 
fineness,  and  were,  probably,  formed  by  the  disintegration  of 
granite.  They  do  not  contain  many  fossils,  and  contain  gold 
in  notable  quantities. 

That  sudden  upliftings  did  occur,  is  shown  by  the  terraced 
structure  at  the  Santa  Cruz  bituminous  deposits,  there  being 
three  terraces  clearly  defined.  The  uprise,  or  face,  of  the  first 
and  second  terraces  was  partly  cut  from  the  bituminous  sands, 
showing  that  the  sands  were  contorted  and  bituminized  before 
these  terraces  were  made  by  the  sea. 


THE    GENESIS   OF    PETROLEUM   AND    ASPHALTUM. 


61 


When  these  bituminized  strata  rose  above  the  line  of  per- 
manent water,  the  flow  of  the  bitumen  was,  and  is  at  the  present 
time,  down  the  dip  of  the  strata  towards  the  sea,  and  the  sands 
in  the  upper  part  of  the  dome,  which  were  vacated  by  the 
bitumen,  are  calcified,  the  lime  probably  being  derived  from 
overlying  calcareous  beds  which  have  been  removed  at  this 
place,  but  which  exist  farther  towards  the  east. 

The  following  is  a  description  of  the  only  explored  submarine 
oil  fields  in  the  world: 


Fig.  16.— Bituminous  Sand  Dipping  Towards  the  Sea. 


In  Santa  Barbara  County,  California,  the  Summerland  oil- 
bearing  strata  consist  of  a  fine-grained  sand,  incased  in  strata 
of  clay  or  clay  slate.  When  near  the  oil-bearing  strata,  the 
clay,  or  slate,  is  of  a  bluish  color,  owing  to  its  being  slightly 
impregnated  with  bitumen.  The  sands  and  shales  form  an 
elongated  dome,  the  longest  axis  of  the  dome  being  from  east 
to  west,  running  nearly  parallel  with  the  coast  and  parallel 
with  the  trend  of  the  Santa  Ynez  Mountains.  Near  the  eastern 
end  of  the  dome  the  formation  dips  about  S.  20°  E.,  at  an 
angle  of  about  50°,  whereas,  on  the  western  end,  the  sand  dips 


62  CALIFORNIA    STATE    MINING   BUREAU. 

about  S.  10°  W.,  at  an  angle  of  about  60°.  The  general  dip  of 
the  sand  is  southerly,  at  an  angle  of  about  40°  or  50°. 

The  first  discovery  of  the  hydrocarbons  in  this  field  was 
made  on  the  south  slope  of  the  anticline.  At  this  place  there 
was  a  fumarole,  some  twenty  feet  in  diameter,  from  which 
warm  carburetted  and  sulphuretted  hydrogen  gas  escaped. 
No  vegetation  grew  on  this  place,  owing  to  the  sulphur 
fumes.  The  Spaniards  had  a  legend  that  a  man  was  killed 
there,  which,  according  to  them,  accounted  for  the  fact  that 
nothing  grew  upon  it.  A  pipe  was  sunk  in  the  fumarole,  and 
capped,  and  a  two-inch  pipe  inserted  in  the  cap,  when  the  gas 
was  permitted  to  flow  through  the  pipe.  It  did  so  with  con- 
siderable pressure,  and,  when  lighted,  gave  a  flame  ten  feet  in 
length.  On  a  line  nearly  east  and  west  with  this  fumarole, 
other  wells  have  been  bored,  which  have  yielded  gas.  The  gas 
has  been  employed  for  domestic  purposes. 

South  of  the  gas  wells,  on  a  nearly  east  and  west  line,  are  a 
line  of  oil  wells;  they  are  from  130  to  260  feet  deep.  The 
flrst  oil  obtained  in  the  field  was  from  a  well  dug  90  feet  in 
depth,  which  produced  three  or  four  barrels  daily.  The  oil  is 
black  or  dark  green,  and  is  of  a  very  heavy  gravity,  being  1 1° 
to  16°  Baume. 

Judging  from  other  oil  fields,  the  northern  dip  of  the  sands 
of  this  anticline  will  be  barren.  Meteoric  water,  falling  on 
the  higher  ground  of  the  Santa  Ynez  Mountains,  which  at 
places  reach  an  altitude  of  3,600  feet,  penetrates  the  earth 
through  inclined  and  porous  strata,  or  through  fissures, 
cracks,  seams,  and  joints.  After  flowing  through  subterranean 
passages,  it  must  ascend  through  permeable  strata  to  the 
surface,  or,  hidden,  find  its  way  to  the  sea.  As  the  Summer- 
land  anticline  forms  a  barrier  between  the  Santa  Ynez 
Mountains  and  the  sea  to  the  passage  of  the  water,  it  is  forced 
by  hydrostatic  pressure  to  ascend  through  the  north  dip  of 
the  sand  of  this  anticline.  Owing  to  its  inferior  gravity,  the 
petroleum  oil  is  floated  upwards  by  the  water,  and  is  lost  on 
the  surface  of  the  earth,  or  is  carried  over  to  the  south  dip  of 
this  anticline.  With  the  southern  dip  of  this  anticline  it  is 
different;  the  flow  of  the  water  is  downwards,  the  oil  remaining 
on  top  of  the  water  by  its  buoyancy. 

Owing  to  the  large  amount  of  organic  matter  in  the  shales 
underlying  the  Summerland  oil  field,  if  any  iron  was  present 


Fig.  17. 


64  CALIFORNIA  STATE   MINING   BUREAU. 

during  their  deposition,  it  must  have  been  in  the  form  of  ferrous 
carbonate.  The  carbonate  of  iron  imparts  a  bluish  or  greenish 
color  to  the  deposit.  When  the  shales,  in  which  carbonate  of 
iron  exist,  are  turned  red,  it  is  caused  by  chemical  heat.  The 
presence  of  red  shales  below  the  Summerland  oil  strata,  as 
revealed  by  a  well  drilled  to  the  depth  of  1,000  feet,  and  the  high 
temperature  of  the  natural  gas,  show  that  chemical  changes 
are  in  active  operation  at  present  beneath  this  field.  It  is 
probable  that  sulphur  compounds,  liberated  by  chemical  heat 
in  the  shales,  have  resinified  the  petroleum  oils  of  Summerland, 
which  will  account  for  their  great  gravity. 

A  wharf  has  been  extended  into  the  sea  towards  the  south, 
and  at  nearly  right  angles  with  the  trend  of  the  shore.  From 
this,  productive  wells  are  drilled  in  the  bottom  of  the  ocean, 
yielding  a  petroleum  oil  somewhat  lighter  than  the  numerous 
wells  upon  the  shore. 

Fig.  17  (page  63)  is  a  profile  made  by  J.  B.  Treadwell,  M.E., 
showing  the  character  and  structure  of  the  rocks  encountered, 
and  the  number  of  wells  which  have  been  drilled. 

The  illustration  Fig.  18  shows  a  formation  lying  east  of  Zaca 
Creek,  in  the  county  of  Santa  Barbara,  California.  A  A  A  is 
bituminized  sand,  forming  the  south  dip  of  an  anticline;  under- 
lying the  bituminous  sand  are  bleached  shales,  B  B  B,  and  below 
the  shales  are  metamorphic  rocks,  quartzite,  and  serpentine. 
At  one  point  the  metamorphic  rock  has  closely  approached  the 
bituminized  sand.  At  this  point  the  bitumen  has  been  removed 
from  the  sand,  and  the  sand  is  calcified  and  silicified.  From 
the  attending  phenomena,  it  would  seem  that  these  sands  were 
bituminized  before  metamorphism  reached  them. 

This  sandstone,  when  not  reduced  by  erosion,  is  xiearly  300 
feet  in  thickness,  and,  like  a  mantle,  covers  a  large  part  of  the 
territory  lying  between  the  Santa  Maria  and  Santa  Ynez  rivers, 
the  Pacific  Ocean  and  the  Alamo  Pintado  Creek,  in  Santa 
Barbara  County,  some  600  square  miles.  In  the  summit  of 
the  domes,  and  in  the  dip  of  the  anticlines  which  are  farthest 
away  from  the  mountains  which  are  higher  than  the  summits 
of  these  anticlines,  the  sands  are  sometimes  bituminized. 
Extending  towards  the  northwest,  from  the  place  shown  in  the 
illustration,  are  sands  containing  millions  of  tons  of  bitumen. 
These  bituminized  sands   are  very  prominent,  forming   high 


THE   GENESIS   OF    PETROLEUM    AND    ASPHALTUM. 


65 


bluffs.  Throughout  the 
area  which  this  upper 
sand  covers,  there  are 
places  where  these  sands 
are  silicified,  in  others  cal- 
cified. 

On  the  south  slope  of 
the  Santa  Maria  Valley, 
and  in  some  other  places, 
these  sands  are  uncement- 
ed,  and  have  been  formed 
into  sand  hills  through 
the  shifting  of  the  sands 
by  water  and  the  winds. 
Also,  scattered  throughout 
this  area,  there  are  a  num- 
ber of  sulphur  blows,  min- 
eral springs,  and  places 
where  natural  gas  escapes 
in  large  quantities.  On 
the  slopes  of  Mount  Solo- 
mon, asphaltum  is  in- 
jected into  the  formation 
surrounding  subsidences. 
Veins  of  asphaltum  also 
occur  on  the  Jonata 
Rancho.  White  leached 
shales,  and  shales  burned 
to  various  tints  of  red, 
occur  in  large  masses. 
The  shales  and  sandstones 
in  this  area  are  fairly  con- 
formable. 

On  the  Sisquoc  River 
there  is  another  exposed 
sand  which  is  bituminized, 
and  which  is,  geologically, 
about  1,000  feet  lower 
than  this  upper  sand,  and 
is  separated  from  it  by  a 
bed  of  shale.  How  thick 
5— b16 


66  CALIFORNIA   STATE   MINING   BUREAU. 

this  lower  sand  is  cannot  be  positively  determined,  but,  judging 
from  its  exposures,  it  must  be  over  300  feet  thick.  If  this  sand 
covers  the  same  area  as  the  upper  sand,  which  it  is  reasonable 
to  suppose  it  does,  there  is  no  reason  why  it  should  not  contain, 
in  its  domes  and  the  dips  of  its  anticlines,  millions  of  tons  of 
bitumen,  which,  on  account  of  being  excluded  from  the  atmos- 
phere, should  be  in  the  form  of  petroleum  oil,  and  which  could 
be  obtained  by  the  sinking  of  wells. 

If  it  be  true  that  the  bitumens  are  derived  from  terrestrial 
and  marine  vegetation,  deposited  in  sedimentary  strata,  and 
then  changed  to  carbonaceous  matter,  which  was  afterwards 
distilled  by  the  heat  of  metamorphism,  then  we  may  expect 
to  find  petroleum  oil  or  other  bitumens  in  unaltered  rocks 
lying  above  the  metamorphic  rocks,  irrespective  of  the  age  of 
the  unaltered  rocks. 

A  number  of  facts  that  have  been  presented  in  the  preceding 
pages  tend  to  prove  that  this  is  the  origin  of  bituminous 
accumulations  in  California. 

A  conclusive  determination  of  the  origin  of  the  bitumens  is 
of  great  importance,  for  if  the  origin  is  as  set  forth  in  this 
monograph,  explorations  can  be  continued  to  such  depths  as 
to  reach  the  metamorphic  rock,  and  these  explorations  may  be 
successful,  especially  so  if  the  bitumens  are  found  near  the 
surface;  but  if  the  bitumens  are  indigenous  to  the  rocks  in 
which  they  are  found,  the  depth  to  which  they  may  extend  is 
uncertain. 

PHENOMENA  ATTENDING  THE  ACCUMULATIONS  OF  BITUMEN. 

The  phenomena  described  in  the  succeeding  pages  are  con- 
nected with  the  accumulations  of  bitumen  as  observed  in  Cali- 
fornia. All  of  these  phenomena  are  generally  found  in  one 
formation,  and  so  frequently  together  and  in  conjunction  with 
bituminous  deposits  that  it  must  be  considered  that  one  is  the 
result  of  or  is  closely  connected  with  the  other,  especially  when 
it  is  known  that  one  can  produce  or  is  the  direct  effect  of  the 
other. 

These  phenomena  would  not  be  important  in  prospecting  for 
a  primary  or  stationary  mineral  deposit,  but  will  be  of  great 
assistance  in  the  discovery  of  a  derived  and  migratory  fluid 
such  as  petroleum  oil. 


THE   GENESIS   OF   PETROLEUM   AND   ASPHALTUM.  67 

When  their  influence,  relation,  and  position  in  regard  to 
bitumens  or*  bituminous  deposits  are  determined  and  more 
generally  understood,  they  will  materially  assist  in  the  dis- 
covery and  development  of  such  deposits. 

Red  shales,  earth  subsidences,  mineral  and  hot  springs, 
leached  shales  and  sandstones,  silicified  shales  and  sandstones, 
and  accumulations  of  bitumen  accompany  one  another  and  are 
traceable  to  metamorphic  action. 

Normal  Shale. — This  is  an  impure  hydrous  silicate  of 
alumina.  It  contains  about  twenty  per  cent  of  alumina,  about 
seventy  per  cent  of  silica,  and,  in  variable  and  small  amount, 
protoxide  and  carbonate  of  iron,  lime,  soda,  magnesia,  potash, 
and  other  minerals,  and  organic  substances.  It  contains  fossils 
in  greater  or  less  number.  Color  of  the  shale  is  usually  dirty 
white  to  brown,  but  sometimes  of  other  colors.  It  gives  out  an 
earthy  odor  when  breathed  upon,  and  is  readily  scratched  wdth 
the  finger  nail.  When  wet  with  water  it  can  be  kneaded  into 
a  plastic  mass.  It  is  clay  consolidated  by  pressure,  and  is 
capable  of  being  split  into  thin  layers  along  the  original  laminae 
of  deposition.  When  exposed  to  atmospheric  influences  it 
rapidly  disintegrates. 

Normal  Sandstones. — When  first  deposited  by  water,  these 
consist  of  incoherent  grains  of  silica  of  different  fineness.  The 
grains  are  more  or  less  rounded  by  attrition,  the  result  of  their 
transportation  by  water.  They  may  contain  fragments  of  other 
rocks,  and  they  may  contain  in  small  quantities  lime,  magnesia, 
potash,  soda,  a  number  of  other  minerals,  and  organic  sub- 
stances. After  deposition,  the  cohesion  of  the  grains  may  be 
effected  by  pressure  alone.  They  may  contain  fossils  in  greater 
or  less  number.     Sandstones  are  of  many  colors. 

Both  shale  and  sandstone  at  the  time  of  their  deposition  may 
be  cemented  by  ferric,  calcareous,  silicious,  or  other  material ; 
but  this  cementation  usually  occurs  subsequent  to  their  deposi- 
tion, when  fresh  or  mineral  waters  commence  to  circulate 
through  them. 

Alterations  in  the  shale  and  sandstone,  effected  by  fresh  and 
mineral  waters,  heat,  and  in  other  ways,  will  be  described 
hereafter. 

The  accompanying  sketch  and  sections  (Figs.  19  and  20) 
show  a  portion  of  the  San  Rafael  Mountains,  situated  in  the 
northern  end  of  Santa  Barbara  County,  State  of  California. 


68 


CALIFORNIA   STATE   MINING   BUREAU. 


The  territory  shown  on  the  map  includes  an  anticline  with 
a  northwest  and  southeast  strike  and  having  a  metamorphic 
core.  The  unaltered  rocks  of  the  anticline  consist  of  alternat- 
ing beds  of  sandstones  and  shales,  and  the  metamorphic  rocks 
principally  of  cherts,  jaspers,  and  serpentines. 

The  metamorphic  rocks  shown  in  the  diagram  and  sections 
once  formed  a  portion  of  the  unaltered  shales  and  sandstones 
r 


L£G£r/\fO 
^^      SH»L£ 


PORTION 
OF  THE 


SAN      RA  FAEL^, 
MOUNTA 1 NS 

SANTA  BARBARA  CO. 


FfG.  19. 


now  forming  these  mountains.  The  unaltered  strata  have 
afforded  casts  of  marine  shells,  considered  by  Dr.  Merriam  as 
pliocene. 

The  broken,  bent,  distorted,  and  warped  condition  of  these 
metamorphic  rocks  has  been  attributed  to  the  movement  of  the 
mass  after  metamorphism  has  taken  place. 

The  broken  condition  and  intricate  jumble  of  these  altered 
shales  and  sandstones  could  not  have  occurred  subsequent  to 


THE   GENESIS   OF   PETROLEUM    AND   ASPHALTUM. 


69 


their  metamorphism.  The  chief  cause  of  the  disturbance  of 
these  rocks  occurred  before  they  were  metamorphosed,  owing 
to  the  contraction  of  the  sandstone  and  shale.  When  burned 
to  a  jasper,  the  overlying  rocks  of  Nature's  kiln  were  continu- 
ally falling  and  subsiding. 

The  face  of  a  bluff  of  shale  or  sandstone  in  which  subsidence 


Fig.  20.— Cross-Section  San  Rafael  Mountains,  Santa  Barbara  County, 
California. 

is  taking  place  is  much  different  in  appearance  from  the  face  of 
a  bluff  composed  of  these  rocks  which  are  being  thrust  upwards, 
or  which  are  subjected  to  lateral  pressure. 

In  subsidences  of  shale  and  sandstone  numerous  cavities  are 
formed  which  are  arched  above,  the  rock  having  fallen  from 
beneath  the  arch.  When  these  arches  break,  the  cavities  are 
filled  with  loose  material. 

These  arched  cavities  do  not  occur  in  formations  which  are 


70  CALIFORNIA   STATE   MINING   BUREAU. 

being  uplifted.  In  subsidences,  cracks  in  the  rocks  which 
approach  horizontality  are  widened  and  the  rocks  fault  on  these 
cracks.     These  cracks  are  not  widened  in  an  upward  thrust. 

Subsidences  are  not  faults;  they  usually  form  a  centrocline, 
and  the  depression  is  always  greater  at  the  center  than  at  the 
periphery;  many  of  the  depressions  are  bowl-shaped,  and  are 
called  "ollas"  by  the  Spaniards.  Many  of  these  depressions 
now  form  the  beds  of  lakes.  In  the  same  area  these  subsi- 
dences are  repeated  many  times.  The  entire  area  does  not 
subside  at  the  same  time,  and  it  is,  therefore,  greatly  broken 
and  crushed;  nor  does  the  movement  take  place  at  one  time, 
but  may  continue  for  years. 

By  the  time  these  shales  and  sandstones  come  in  contact 
with  metamorphic  heat  they  are  badly  broken  and  contorted, 
owing  to  the  action  of  subsidence,  and  they  are  further  warped 
and  twisted  by  the  heat  of  metamorphism. 

At  a  depth  of  500  to  1,000  feet  the  subsidence  due  to  coal 
workings  amounts  to  about  fifty  per  cent  of  the  thickness  exca- 
vated; sometimes  these  subsidences  continue  during  as  much 
as  four  years.  The  contraction  in  a  formation  composed  of 
equal  volumes  of  shales  and  sandstones  when  burned  to  a  por- 
celanite,  is  about  one  tenth  of  its  original  volume.  A  forma- 
tion burned  to  a  depth  of  1,000  feet  would  give  a  subsidence  on 
the  surface  of  100  feet  in  depth,  or,  taking  the  amount  of  subsi- 
dence as  is  shown  in  coal  workings,  would  give  a  subsidence  of 
50  feet  in  depth. 

The  red  shales  and  porcelanites  previously  described  nearly 
always  accompany  these  subsidences.  If  the  interspaces  exist- 
ing in  these  red  shales  were  filled  with  soluble  silica,  they 
would  become  jaspers  of  many  colors. 

The  presence  of  comminuted  red  shale  in  the  oils  at  Summer- 
land,  Santa  Barbara  County,  California,  and  the  striking  of  red 
shales  at  the  same  place  at  a  depth  of  1,000  feet,  show  that  these 
shales  exist  at  great  depths. 

Scattered  throughout  Santa  Barbara*  County  are  over  one 
thousand  acres  which  have  undergone  subsidence,  and  some  of 
which  are  still  subsiding.  The  amount  of  depression  is  from 
20  to  60  feet,  with  an  average  of  40  feet,  and  there  may  be 
many  more  acres  which  have  undergone  subsidence  that  have 
escaped  observation,  or  which  are  or  were  not  visible  on  the 


THE  GENESIS  OF  PETROLEUM  AND  ASPHALTUM. 


71 


surface,  or,  if  visible,  all  signs  of  the  subsidence  have  been 
obliterated. 

Near  the  north  line  of  the  Sisquoc  Rancho,  on  La  Brea  Creek, 
Santa  Barbara  County,  the  blufl'  on  the  west  side  of  the  creek 
is  over  300  feet  high,  and  over  a  mile  long,  and  covers  an  area 
exceeding  three  hundred  acres.  The  entire  bluff  is  badly  broken 
and  contorted,  and  shows  evidences  of  subsidence,  even  now 
going  on. 


Fig.  21.— Subsidence,  La  Brea  Creek. 

Chemical  heat  reddens  and  bakes  and  vitrifies  the  shales  at 
the  bottom  of  the  bluff.  The  surrounding  shales  are  blackened 
with  carbonaceous  matter.  Fig.  21  shows  the  southern  end  of 
the  bluff.  Surrounding  this  subsidence  are  hundreds  of  acres 
of  shales  which  have  been  silicified. 

In  the  vicinity  of  nearly  all  these  subsidences,  burned  and 
leached  shales  and  sandstones  are  found. 

The  breaking  and  contortion  of  the  metamorphic  rocks  have 


72  CALIFORNIA   STATE   MINING   BUREAU. 

been  attributed  to  the  dynamic  force  exerted  in  the  uplifting 
and  plication  of  the  mountains.  While  this  force  is  responsi- 
ble for  this  broken  and  contorted  state  in  part,  the  greater  part 
must  have  been  effected  by  subsidence  and  the  warping  of  the 
rocks  by  the  heat  of  metamorphism. 

The  curvature  in  the  altered  rocks  is  too  acute  and  in  the 
wrong  direction,  and  the  fragments  of  the  rocks  bent  too  small, 
to  have  been  made  by  the  uplifting  of  the  rocks. 

Attending  the  uplifting  and  the  metamorphism  of  mountains 
there  must  have  been  subsidences  of  the  superincumbent  unal- 
tered rocks  to  fill  the  space  caused  by  the  contraction  of  the 
rocks  through  the  action  of  heat. 

The  breaking  and  division  of  the  unaltered  rocks  lying  above 
and  adjoining  the  places  where  metamorphic  action  is  in 
progress  facilitate  metamorphic  changes.  It  is  like  the  placing 
of  broken  coals  upon  a  fire:  the  interspaces  between  the  pieces 
permitting  the  circulation  of  gases,  minerals,  and  heat. 

Water. — Through  its  inferior  gravity,  petroleum  oil  ascends 
through  water  from  the  depths  of  the  earth,  and  either  forms 
bituminous  springs  upon  the  surface  of  the  earth,  or,  by  its 
buoyancy,  floats  upon  the  water  and  is  stored  in  the  upper 
parts  of  porous  or  seamed  strata.  The  movement  of  subter- 
ranean water  is  indicative  of  the  movement  of  oil.  Besides 
these  offices,  the  influence  which  thermal  waters  holding  silica 
and  other  minerals  in  solution  have  exerted  in  many  rocks  is  a 
question  closely  connected  with  the  accumulations  of  the 
bitumens.  All  deposits  precipitated  from  water — lime,  silica, 
etc. — may  become  the  cementing  substance  of  shale  or  sand- 
stone; and,  again,  all  substances  cementing  or  composing  rocks 
which  are  soluble  in  water  are  liable  to  be  leached  from  the 
rocks  by  percolating  water.  There  may  be  mineral  springs 
without  the  presence  of  bitumen,  but  there  are  no  springs  of 
bitumen  that  are  not  accompanied  by  mineral  waters. 

Southwest  of  the  metamorphic  rock  shown  in  Fig.  19  are 
sandstone  strata,  and  farther  to  the  west  is  shale.  The  sand- 
stone, where  it  adjoins  the  serpentine,  is  snow  white.  Hot 
alkaline  and  acid  waters  entered  these  shales  and  sandstones 
and  dissolved  the  bases  contained  in  them,  also  dissolving  a 
quantity  of  silica.  These  waters  cooled  as  they  neared  the 
surface.    The  silica   would  have    been    deposited    had   these 


THE   GENESIS   OF   PETROLEUM   AND   ASPHALTUM. 


73 


waters  not  encountered  a  flow  of  meteoric  water,  which  greatly- 
diluted  the  hot  solution.  This  increased  volume  of  water  made 
it  possible  for  the  silica  and  bases  to  be  held  in  solution  and  be 
carried  away  to  the  sea. 

The  shales  become  darker  as  they  go  from  the  altered  rocks, 
until  they  finally  assume  the  color  of  normal  shale.  In  places 
these  leached  shales  have  a  width  exceeding  one  mile. 

The  arrows  in  the  sectional  views  indicate  the  direction  in 


Fig.  22.— Contact  of  Leached  Sandstones  and  Serpentine. 

which  the  water  flowed  and  the  general  direction  in  which  it 
now  flows.  The  geographical  configuration  of  the  country 
shows  that  the  waters  flowed  in  this  direction,  as  higher  moun- 
tains lie  to  the  north  of  the  formation  shown  in  the  sectional 
views.  The  finding  of  bitumen  in  the  southern  dip  and  the 
absence  of  the  same  from  the  northern  dip  of  the  anticline 
shown  in  section  C  D  is  additional  proof  that  waters  flowed  in 
the  direction  shown  by  the  arrows.     (See  Fig.  20.) 

Near  the  serpentine  all  fossil  shells  are  removed  from  the 
shales  and  sandstones  by  the  solvent  action  of  mineral  waters, 


74  CALIFORNIA    STATE    MINING   BUREAU. 

and  the  casts  and  molds  are  obliterated  through  the  incoher- 
ency  of  said  sandstones  and  shales,  and  also  by  the  removal  of 
the  coloring  from  the  darker  material  that  usually  replaces  the 
part  formerly  occupied  by  the  shell.  At  a  distance  of  a  thou- 
sand feet  or  more  from  the  serpentine,  the  same  stratum  that 
adjoins  the  metamorphic  rocks  contains  casts  and  molds  of 
fossil  shells,  while  still  farther  away  fossil  shells  exist. 

The  whitened  shales  have  a  porous  structure,  and  are  very 
light  compared  with  normal  shales.  They  can  be  easily  ground 
between  the  fingers,  owing  to  the  removal  of  soluble  material 
which  once  occupied  the  pores. 

Shales  and  sandstones  leached  of  all  bases,  such  as  lime, 
magnesia,  metals,  etc.,  are  but  slightly  coherent  and  are  easily 
eroded. 

Jaspers. — The  metamorphic  rocks  shown  in  the  sketch  con- 
sist principally  of  jaspers,  or  shales,  and  sandstones  partly 
converted  to  jaspers.  They  have  a  hardness  of  7  and  a  specific 
gravity  of  2.55,  and  break  with  a  conchoidal  fracture.  Their 
prevalent  colors  are  yellow  and  brownish  red  of  various  shades, 
sometimes  nearly  black  in  the  seams,  and  sometimes  a  greenish 
white.  The  darker  jaspers  often  have  a  resinous  luster,  but 
are  generally  dull. 

The  transition  from  shale  to  jasper  is  plainly  visible;  all 
gradations  from  unaltered  shale  to  jasper  will  occur  within  a 
distance  of  a  few  feet.  A  portion  of  the  jaspers  retains  the 
form  of  shales,  with  the  exception  that  they  are  contracted  and 
distorted  by  heat.  Sometimes  they  are  burned  so  as  to  form  a 
solid  mass.  After  burning,  they  have  been  silicified  with  amor- 
phous silica,  filling  minute  cracks  and  spaces  in  the  jaspers. 

The  brownish-red  jaspers  show  unmistakable  signs  of  having 
been  burned.  They  are  warped,  contracted,  broken,  and  vesicu- 
lar, showing  all  the  structural  conditions  that  shale  does  when 
artificially  burned  in  large  masses. 

The  whitish-green  jaspers  do  not  show  all  these  signs  of 
burning,  even  when  in  immediate  contact  with  the  brownish- 
red  jaspers;  but  the  shales,  between  which  and  the  brownish- 
red  jaspers  these  whitish-green  jaspers  lie,  are  contorted  by 
heat,  and  next  to  the  whitish-green  jaspers  are  discolored  by 
oxide  of  iron. 

The  vesicular  condition  only  occurs  when  the  brownish-red 
shales  are  apparently  greatly  burned. 


THE    GENESIS   OF    PETROLEUM    AND    ASPHALTUM. 


75 


In  places  these  brownish-red  jaspers  closely  resemble  the 
jaspers  that  are  the  most  burned  and  which  are  produced  by 
chemical  heat  near  the  surface  of  the  earth,  and  probably  are 
produced  by  the  same  metamorphic  actions,  but  on  a  greater 
scale. 

Pockets  containing  burned  shales  not  exceeding  eight  inches 
in  diameter  are  found  in  unaltered  shales  near  the  surface, 
which  closely  resemble  some  of  the  jaspers  that  are  in  the 
large  mass  of  metamorphic  rocks  shown  in  the  sketch  (Fig.  19). 

It  might  be  expected  that,  through  metamorphic  agencies, 
jaspers  might  be  formed  in  a  large  space,  but  it  is  remarkable 
that  they  can  be  formed  in  a  space  six  inches  in  diameter. 


Fig.  23.— Open  Seams  at  Right  Angles  to  Planes  of  Bcdding. 

Overlying  the  serpentine  and  jaspers  at  J  (see  Fig.  20)  are 
chemically  burned  shales;  these  burned  and  red  shales  are 
previously  described. 

In  Santa  Barbara  County  these  red  shales  cover  a  large  area. 

Frequently,  in  the  jaspers,  seams  and  cracks  approaching 
horizontality  are  closed,  while  those  approaching  verticality 
are  open  to  the  extent  of  the  contraction  of  the  rocks  during 
burning.  (See  Figs.  23  and  24.)  The  closing  of  the  hori- 
zontal cracks  and  seams  may  be  due  to  the  weight  of  the 
metamorphosed  rocks,  but  it  must  have  been  augmented  by 
other  superincumbent  strata.  The  opening  of  the  vertical 
seams  and  cracks  must  have  occurred  at  the  time  they  were 


76 


CALIFORNIA   STATE   MINING   BUREAU. 


metamorphosed,  showing  that  there  was  no  great  lateral 
pressure  on  the  rocks  during  or  since  their  change. 

The  open  cracks  and  seams  are  either  with,  or  at  right  angles 
with,  the  plane  of  bedding  of  the  rocks.  When  the  plane  of 
bedding  is  nearly  horizontal,  the  open  cracks  are  nearly  verti- 
cal; when  the  plane,  of  bedding  is  nearly  vertical,  the  open 
cracks  are  along  the  plane  of  bedding. 

There  are  three  important  changes  during  the  production  of 
jasper,  or  chert,  from  shale,  viz:  leaching,  baking  or  burning, 
and  silicification,  and  these  changes  occur  in  the  order  given 
above. 


Fig.  24.— Open  Seams  with  Planes  of  Bedding. 

The  leaching  of  lime,  magnesia,  and  other  bases  by  perco- 
lating hot  waters  leaves  a  light  and  porous  rock,  consisting 
principally  of  insoluble  silica  and  alumina. 

The  porous  condition  of  the  rock  permits  the  circulation  of 
heat  and  hot  gases;  this  circulation  of  heat  and  gases  is  also 
aided  by  the  breaking  of  the  formation  through  subsidence. 

When  burnt  by  chemical  fires  these  shales  are  of  many 
shades  of  pink,  red,  reddish  brown,  white  and  yellowish  white, 
and  are  sometimes  black,  this  color  being  caused  by  the 
presence  of  carbonaceous  matter.  Some  of  these  shales  are 
fused   and  are   of  a   brownish  red  to  black;  by  fusion   they 


THE    GENESIS   OF    PETROLEUM    AND    ASPHALTUM.  77 

became  impervious  to  fluids,  while  the  remainder  of  the  shales 
remain  more  or  less  porous. 

Besides  the  cracks  caused  by  earth  movements  there  are 
numerous  small  cracks  caused  by  the  burning  and  breaking. 

One  layer  of  jasper  is  a  bad  misfit  with  the  adjoining  layer. 
Sometimes  a  piece  of  a  layer  of  jasper  a  few  inches  in  length 
will  be  warped  in  one  direction,  whereas  an  adjoining  piece  of 
a  layer  will  be  warped  in  a  contrary  direction;  some  are 
acutely  bent,  but  the  layers  of  jasper  seldom  fit  perfectly  with 
one  another.  Nothing  but  baking  and  burning  could  create 
this  almost  universal  misfit  in  the  layers. 

After  the  jaspers  are  hardened  they  cannot  be  contorted  and 
bent.  They  would  break  before  bending,  and  if  they  were 
contorted  and  twisted  when  in  a  plastic  condition  they  would 
probably  exhibit  slickensides  and  would  have  but  few  wide 
seams  and  seams  of  irregular  width  and  would  not  be  vesicular. 

No  slickensides  are  to  be  seen  between  the  layers,  the  surface 
of  these  layers  being  nearly  always  rough.  The  greatly  con- 
torted, bent,  and  roughly  seamed  condition  of  the  jaspers  must 
have  been  occasioned  by  heat  which  baked,  burned,  fused,  con- 
torted, cracked,  warped,  and  hardened  them  and  made  them 
vesicular. 

Subsequent  to  their  burning  the  small  vesicles  and  cracks  in 
them  were  filled  with  chalcedonic  silica.  On  account  of  their 
burning  and  silicification  they  greatly  resist  weathering. 

Subsequent  to  their  leaching,  burning,  and  baking,  in  some 
of  these  burned  shales  the  vesicles  produced  by  fusion,  and  the 
small  cracks  and  pores  and  numerous  minute  round  and  oval 
areas,  have  been  filled  with  soluble  silica  deposited  from  circu- 
lating silicious  waters,  forming  jaspers  and  cherts. 

These  spaces  are  usually  filled  with  silica,  which  has  a 
difierent  color  from  the  ground  mass  of  the  rock,  the  colors 
usually  being  white  and  of  various  shades  of  red  or  brownish 
red. 

Sometimes  these  interspaces  have  been  filled  with  bands  of 
different  colored  soluble  silica,  the  bands  running  parallel  "ivith 
the  walls  of  the  spaces. 

The  interstices  in  the  strata  of  sandstone  shown  in  section 
E  F  (Fig.  20)  have  been  filled  with  soluble  silica,  making  a 
hard,  compact  rock;  whereas,  the  same  strata  a  short  distance 
to  the  east  and  west  consist  of  sand  cemented  with  bitumen. 


78  CALIFORNIA   STATE   MINING    BUREAU. 

Serpentine  Rocks. — On  the  periphery  of  the  jaspers,  and 
between  the  jaspers  and  unaltered  rocks,  are  serpentine 
rocks;  also  resting  upon  the  jaspers  are  isolated  bodies  of 
serpentine  rocks.  All  gradations  from  shale  to  serpentine 
rocks  can  be  seen.  Shales  having  a  slight  bluish-green  tint 
can  be  obtained;  also  pieces  of  the  shale  partly  converted  into 
serpentine  rock,  one  part  being  serpentinous  and  the  other  shale. 
The  serpentine  rock  lying  on  the  surface  of  the  jaspers  would 
have  a  tendency  to  prove  that  the  said  serpentine  is  not 
eruptive,  but  metamorphic.  Serpentine  is  seen  in  every  stage 
of  passage  from  argillaceous  sandstone,  shale,  and  jasper  to 
perfect  serpentine  itself. 


Fig.  25. 

The  spaces  between  the  irregular  but  somewhat  cubical  frag- 
ments of  jasper,  which  are  arranged  in  rows  after  being  con- 
verted to  jasper  from  shales,  are  filled  with  serpentine  rock,  and 
these  fragments  are  frequently  partly  rounded  by  the  alteration 
of  the  jaspers  to  serpentine  rock.  The  lined  portion  of  the 
cut  (Fig.  25)  indicates  unaltered  jasper,  and  the  remainder  is 
serpentine  rock.  The  rounding  of  the  cubiform  fragments  of 
jasper  represents  an  incipient  decomposition  of  the  same. 

The  serpentine  rock  being  next  to  the  unaltered  rocks,  which 
at  one  time  were  saturated  with  mineral  water,  the  said 
unaltered  rocks  would  permit  the  circulation  of  water  bearing 
these  minerals.  The  decomposition  of  jasper  and  shale  to 
serpentine  rocks  seems  to  be  more  the  action  of  hydrothermal 
than  dry  heat. 

In  places  the  spaces  between  the  fragments  of  shales  and  ser- 
pentine rocks  are  filled  with  quartz  carrying  a  notable  amount 
of  copper  pyrites  and  a  small  amount  of  gold  and  silver.  By 
an  examination  of  the  sectional  views  and  sketch  it  will  be 
seen  that  the  northern  side  of  the  metamorphic  rocks  cuts  the 


THE  GENESIS   OF   PETROLEUM   AND   ASPHALTUM.  79 

strike  of  the  unaltered  rocks  diagonally,  and  that  on  the  south 
side  they  run  parallel  with  the  strata  of  the  unaltered  rocks, 
sandstone  being  in  contact  with  the  serpentinic  rocks. 

A  sectional  view  shows  that  the  unaltered  rocks  on  the  south 
are  part  of  the  same  strata  as  the  unaltered  rocks  lying  on  the 
north  of  the  metamorphic  rocks.  The  unconformity  of  the 
metamorphic  rocks  with  the  sandstones  and  shales  on  the 
north,  and  their  conformity  with  the  sandstones  and  shales  on 
the  south,  taken  with  other  phenomena  described  in  this  arti- 
cle, clearly  demonstrate  the  fact  that  these  unaltered  rocks 
were  not  deposited  on  the  altered  rocks  after  they  were  meta- 
morphosed. The  unaltered  shale  underlying  a  sandstone  is  of 
great  thickness,  whereas  at  a  point  half  a  mile  east  of  this 
sectional  view  the  metamorphic  rock  is  nearly  in  contact  with 
the  same  sand  stratum. 

Northeast  of  the  metamorphic  rocks  are  alternating  beds  of 
shale  and  sandstone.  The  shales  are  highly  silicated.  Silica 
dissolved  in  hot  waters  slowly  ascended  through  the  unaltered 
rocks  lying  north  of  the  metamorphic  rocks.  The  metamorphic 
rocks  acted  as  a  dam  for  its  retention,  and  as  these  hot  waters 
cooled  they  were  incapable  of  holding  the  same  amount  of 
silica  in  solution  as  when  hot;  therefore,  silica  was  deposited 
in  the  interspaces  of  the  porous  rocks.  When  silicious  waters 
flow  upward  through  a  formation  the  rocks  are  silicated,  and 
when  the  water  flowed  or  flows  downward  through  a  formation 
the  rocks  are  leached. 

There  are  several  reasons  why  this  occurs.  When  waters 
flow  upward  their  flow  is  generally  very  slow;  when  coming 
from  the  depths  of  the  earth  the  waters  are  generally  hot,  grad- 
ually cooling  as  they  approach  the  surface,  and  as  they  cool 
silica  is  deposited. 

Silica  is  soluble  in  cold  water.  Under  pressure  and  heat 
the  solvent  power  of  water  is  greatly  increased.  Upon  the 
relief  of  the  pressure  or  the  cooling  of  the  hot  silicated  water, 
silica  is  deposited.  A  solution  of  silicate  of  soda,  when  undis- 
turbed for  a  year  or  more,  will  deposit  silica;  if  frequently 
disturbed,  no  such  deposition  takes  place.  The  deposition  of 
silica  from  such  a  solution  is  quickened  by  the  presence  of 
carbonic  acid.  Petrified  wood  is  often  found  in  rocks  that  are 
not  silicated.  This  is  owing  to  the  fact  that  the  capillary 
tubes  in  the  wood  are  much  smaller  than  the  interspaces  in 


80  CALIFORNIA   STATE   MINING   BUREAU. 

the  circumjacent  rock.  Water  filters  through  the  wood  and 
these  rocks  more .  or  less  quickly  in  proportion  to  their 
permeability;  consequently,  circulation  of  fluids  is  slower  in 
the  wood  than  in  the  adjoining  rocks. 

Rapid  percolation  of  silicious  waters  through  a  rock  prevents 
the  deposition  of  silica.  Shales  and  other  substances  contain- 
ing small  pores  are  very  frequently  silicated,  whereas  the 
adjoining  sandstones  or  coarse  substances  are  still  porous.  The 
greater  porosity  of  the  sandstones  and  other  coarse-grained 
substances  permit  a  too  rapid  flow  of  the  silicious  water,  and 
silica  is  not  deposited;  whereas,  since  the  percolation  of 
silicious  water  in  the  fine  shale  or  other  fine-grained  sub- 
stances is  extremely  slow,  silica  is  deposited.  When  these 
cherty  shales  are  black  it  shows  that  bitumen  was  ascending 
with  the  silicious  waters  at  the  time  they  were  silicated.  After 
being  silicated  they  do  not  split  along  the  plane  of  original 
deposition.  Their  hardness  is  7.  Their  black  color  is  destroyed 
by  fire,  showing  that  their  color  is  due  either  to  a  bituminous 
or  a  carbonaceous  substance.  It  is  in  all  probability  the 
former,  as  carbonaceous  matter  does  not,  whereas  bituminous 
matter  does,  accompany  the  flow  of  silicious  waters.  In  many 
places  these  blackened  and  silicated  shales  adjoin  cracks  and 
seams,  through  which  mineral  water  accompanying  bitumen 
is  ascending. 

Zaca  Peak  owes  its  prominence  to  the  protection  of  a  crown 
of  cherty  shale;  in  fact,  the  preservation  of  this  mountain 
range  is  owing  to  its  silicification,  which  must  have  occurred 
before  it  rose  above  permanent  water;  whereas,  several  thousand 
feet  of  sediments  lying  to  the  southwest  of  the  same  have  been 
denuded  in  consequence  of  being  leached  and  broken. 

Silicated  shales  and  sandstones  are  not  easily  eroded,  and 
suffer  but  slight  decomposition  through  the  action  of  the 
weather.  The  sandstone  is  not  indurated  to  the  same  extent 
as  the  shale.  The  face  of  the  shales  is  flatter  than  the  face  of 
the  sandstones;  the  sandstones  are  nearly  vertical.  Frequently 
these  cherty  shales  contain  many  small  faults  and  cracks,  the 
character  of  which  shows  that  they  were  made  while  the  shale 
was  in  a  semi  plastic  condition.  They  have  been  silicated 
subsequent  to  their  faulting  and  cracking,  clearly  showing 
that  shales  were  silicated  after  the  formation  had  been  greatly 
disturbed.    The  alteration  of  these  white  shales  has  been  partly 


GENESIS   OF    PETROLEUM   AND   ASPHALTUM.  81 

caused  by  baking,  through  the  heat  of  adjacent  metamorphic 
rocks.  Joints  and  seams  in  the  shales  and  spaces  in  the  sand- 
stones are  colored  red  with  the  oxide  of  iron. 

In  part  of  the  bituminized  sands  lenticular  pieces  of  shale 
are  found  converted  into  chert,  and  fossil  shells  have  been 
removed.  These  silicated  lenticular  pieces  of  shale  were  sili- 
cated  after  being  water-worn,  as  their  exteriors  have  all  the 
appearances  of  shale.  If  they  had  been  changed  to  chert 
before  being  water-worn,  they  would  have  had  a  polished  sur- 
face. They  show  the  laminae  of  deposition,  but  do  not  split 
along  them. 

The  insoluble  silica  in  the  pieces  of  shale  consists  of  fine 
quartz  sand  which  composed  the  original  shale,  whereas  the 
soluble  silica  was  deposited  in  the  pores  of  the  shale  from  infil- 
trating water.  These  fragments  of  shale  were  silicified  before 
the  interspaces  of  the  sand  were  filled  with  bitumen,  as  the 
circulation  of  water  ceased  after  the  appearance  of  the  bitumen. 
For  the  same  reason  fossil  shells  must  also  have  been  leached 
from  the  sands  before  they  were  filled  with  bitumen.  Therefore, 
these  sands  were  bituminized  after  their  deposition,  and  must 
have  been  bituminized  before  they  were  tilted  to  the  high  angles 
which  they  now  occupy,  and  before  the  metamorphic  rocks 
came  in  contact  with  them. 

The  bituminized  sand  near  Zaca  Creek  contains  at  least  ten 
million  barrels  of  maltha.  Eight  barrels  of  ordinary  petro- 
leum are  required  to  make  one  barrel  of  maltha.  As  the  inter- 
spaces of  the  bituminous  sand  are  filled  with  maltha,  a  space 
ten  times  as  large  as  the  present  bituminous  deposit  was 
required  to  accommodate  eighty  million  barrels  of  petroleum 
before  it  was  changed  to  maltha.  The  apex  of  the  anticline 
lying  above  the  metamorphic  rock,  when  the  curvature  of  the 
rocks  was  slight,  must  have  been  the  storage  room  for  this 
vast  amount  of  petroleum.  When  the  strata  of  this  anti- 
cline containing  the  petroleum  slowly  rose  above  permanent 
water,  and  owing  to  the  fact  that  the  anticline  rose  to  a  higher 
altitude  in  the  east  than  in  the  west,  the  oil  flowed  down  the 
porous  strata  towards  the  west,  and  during  the  flow  was  evapo- 
rated, forming  maltha,  which  finally  reached  its  present  resting 
place.  During  this  migration  of  the  oil,  besides  the  amount 
dissipated  by  evaporation,  a  vast  amount  must  have  been 
6— Bl6 


82  CALIFORNIA    STATE    MINING    BUREAU. 

carried  away  b}^  percolating  waters  or  drained  from  the  porous 
strata  and  was  lost. 

In  1864  a  multitude  of  fish  were  asphyxiated  in  the 
Pacific  Ocean  and  came  ashore  between  Monterey  and  Ven- 
tura in  large  quantities.  Many  were  dead  and  others  were 
barely  alive.  This  was  probably  occasioned  by  the  ocean 
waters  being  charged  with  sulphuretted  hydrogen  or  carbonic 
acid.  These  mephitic  gases  emanated  from  metamorphic 
action  beneath  the  ocean,  ocean  currents  and  migratory  habits 
of  the  fish  submerging  them  in  the  deadly  waters.  In  1899 
the  fish  were  killed  in  Zaca  Lake  by  sulphuretted  hydrogen, 
the  presence  of  sulphuretted  hydrogen  being  evidenced  by  the 
whitish  state  of  the  water,  caused  by  the  liberated  sulphur. 
The  Indians  had  a  number  of  superstitions  regarding  this  lake, 
which  were  probably  occasioned  by  former  phenomena  which 
appeared  supernatural  to  them. 

Conclusions. — Black  or  dark-colored  cherty  shales  and  sand- 
stones show  that  bitumen  accompanied  the  silicious  waters 
while  these  rocks  were  being  silicated.  Light-colored  cherty 
shales  and  sandstones  show  the  absence  of  bitumen  during 
their  silicification.  These  cherty  shales  and  sandstones  indicate 
either  that  silicious  waters  have  cooled  while  ascending  towards 
the  surface,  or  that  the  circulation  of  the  silicious  water,  gen- 
erally upwards  through  them,  has  been  very  slow.  Both  these 
flows  of  water  would  have  a  tendency  to  remove  petroleum 
from  a  formation  if  any  had  existed  therein.  If  bitumen 
deposits  exist  in  a  formation  the  leached  shales  and  sandstones 
usually  overlie  them,  although  white  leached  shales  and  sand- 
stones may  exist  where  there  is  no  bitumen. 

PROSPECTING  FOR  PETROLEUM. 

Surface  indications  of  the  presence  of  petroleum  consist  of 
unaltered  rocks,  white-leached  shales  and  sandstones,  shales 
burnt  to  redness,  fumaroles,  mineral  springs  and  the  residue 
from  mineral  springs,  such  as  selenite,  etc.,  subsidences,  natural 
gas,  springs  of  petroleum  oil  and  maltha,  porous  rocks  saturated 
with  bitumen,  cracks  in  shale  and  other  rocks  filled  or  partly 
filled  with  bitumen,  black  silicified  shales. 

It  would  seem  like  supererogation  to  say  that  petroleum  oil  is 
not  found  in  any  notable  quantity  in  metamorphic  rocks,  and 


GENESIS   OP    PETROLEUM    AND   ASPHALTUM.  83 

if  found  at  all  that  it  is  a  secondary  deposit.  One  may  as  well 
expect  to  find  accumulations  of  petroleum  in  a  limekiln  as  in 
metamorphic  rocks,  yet  notwithstanding  this  fact,  which  one 
would  think  would  be  patent  to  every  person,  wells  for  oil  have 
been  drilled  in  granite.  The  prospector  should  confine  his 
attention  to  unaltered  rocks. 

The  color  of  the  bitumens,  when  they  exist  near  the  surface 
of  the  earth,  is  black,  bluish  black,  and  brown  and  dirty  brown. 
The  bitumen  can  be  determined  from  coal,  vegetable  deposits, 
iron,  manganese,  and  other  minerals  that  closely  resemble 
them,  by  the  following  tests:  By  its  bituminous  odor  and  taste; 
by  melting  in  the  flame  of  a  match  or  candle  with  a  bituminous 
odor  (iron  and  manganese  do  not  fuse,  and  coal  and  vegetable 
matter  burn  without  fusion) ;  by  dissolving  in  bisulphide  of 
carbon,  chloroform,  and  turpentine. 

It  would  be  well,  in  prospecting  for  oil,  to  carry  a  small 
bottle  of  one  of  these  solvents  and  another  small  bottle  in 
which  the  substance  to  be  determined  is  placed  in  a  com- 
minuted form  and  agitated.  If  a  brown  or  black  solution  is 
formed,  the  substance  under  examination  is  bitumen.  Iron, 
manganese,  coal,  and  vegetable  matter  do  not  dissolve  in  these 
solvents. 

All  streams,  pools,  and  other  bodies  of  water  should  be  care- 
fully inspected.  If  oil  is  present  it  will  float  on  the  surface, 
showing  prismatic  colors.  Compounds  of  iron  floating  on  the 
surface  of  water  frequently  show  these  iridescent  colors. 
Whether  this  scum  is  oil  or  an  iron  compound  can  be  deter- 
mined by  stirring  the  surface  of  the  water  with  a  circular 
motion.  If  iron,  the  scum  will  break  into  irregular  fragments, 
and  if  oil  it  will  form  bands  of  color.  In  other  words,  the  iron 
compound  seems  to  act  and  break  like  a  solid,  whereas  the  oily 
scum  acts  like  a  liquid. 

Frequently  gases  are  seen  to  ascend  from  the  bottom  of 
streams  and  pools  of  water.  In  the  bed  of  La  Brea  Creek,  upon 
the  Sisquoc  Rancho,  Santa  Barbara  County,  gases  rise  from 
the  bottom  of  the  creek  for  a  distance  exceeding  one  mile, 
which  can  be  lit  upon  the  surface  of  the  water  and  burn  with 
a  luminous  flame.  This  occurs  in  many  other  places  in 
California. 

Carburetted  hydrogen,  or  natural  gas,  is  a  far  greater  indi- 
cation of  the  presence  of  the  bitumens  than  is  sulphuretted 


84 


CALIFORNIA    STATE    MINING    BUREAU. 


hydrogen  or  carbonic  acid  gas;  consequently,  it  is  frequently 
important  to  determine  between  these  gases.  Carburetted 
hydrogen  burns  with  a  yellow,  luminous  flame,  whereas 
sulphuretted  hydrogen  burns  with  a  bluish  flame.  A  familiar 
example  of  the  color  of  these  flames  is  shown  in  the  burning  of 
an  ordinary  match.  Light  the  match,  and  while  the  sulphured 
end  is  burning  a  bluish  flame  is  shown.  When  the  sulphur  is 
consumed  and  the  wood  alone  burns,  a  luminous  flame  is 
shown.  Sulphuretted  hydrogen  has  a  strong  odor  of  sulphur, 
and  when  a  brightened  piece  of  silver  is  held  in  it  the  silver 

becomes  blackened.     Carbonic  acid 
gas  does  not  burn. 

The  test  papers  described  below 
should  be  obtained  and  kept  dry  and 
well  protected  both  from  air  and 
light,  which  can  be  done  by  keeping 
them  in  a  small,  wide-mouthed  bot- 
tle of  dark  glass. 

First — Acetate  of  lead  paper, 
which,  when  exposed  to  gas  con- 
taining sulphuretted  hydrogen, 
becomes  darkened  and  eventually 
brown;  if,  after  an  exposure  of  ten 
minutes,  the  paper  does  not  become 
discolored,  the  gas  may  be  consid- 
ered free  from  sulphuretted  hydro- 
gen. 

Second — Blue  litmus  paper,  when 
used,  should  be  moistened  with  pure 
water;  when  exposed  to  carbonic 
acid  gas,  or  water  highly  charged 
with  carbonic  acid  gas,  it  turns  red. 
The  tests  with  the  papers  can  be  made  as  follows,  this  explana- 
tion referring  to  Fig.  26: 

Procure  an  ordinary  beer  bottle  of  clear  glass;  run  a  red-hot 
poker  several  times  around  and  near  the  bottom  of  the  bottle; 
dip  the  bottle  into  cold  water,  and  the  bottle  will  break  at  the 
line  where  the  hot  poker  has  been  applied.  Stop  the  bottle  with 
a  cork,  through  which  the  small  hole  A  has  been  made.  The 
test  paper  B  is  suspended  in  the  bottle  by  a  wire  fastened  in 
the  cork.     Leave  the  hole  A  open  and  hold  the  lower  and  open 


Pig.  26. 


GENESIS   OF   PETROLEUM   AND    ASPHALTUM.  85 

end  of  the  bottle  partly  submerged  in  the  water  and  over  the 
bubbles  of  gas  which  are  ascending  through  the  water.  If  sul- 
phuretted hydrogen  or  carbonic  acid  is  present  they  will  act  in 
the  manner  described  above  on  the  respective  test  papers  which 
are  used  to  detect  their  presence.  These  papers  will  show  the 
absence  of  sulphuretted  hydrogen  and  carbonic  acid  gas,  but 
where  they  are  mixed  with  carburetted  hydrogen  the  other 
tests  will  have  to  be  employed,  such  as  the  color  of  the  flame 
when  burning  to  determine  whether  carburetted  hydrogen  is 
present. 

To  make  the  test  by  the  color  of  the  flame:  Open  the  hole  A 
and  submerge  the  entire  bottle  in  the  water;  after  the  bottle  is 
filled  with  water,  close  the  hole  A  and  lift  the  bottle  nearly  out 
of  the  water;  the  bottle  will  remain  full  of  water,  on  account 
of  atmospheric  pressure;  hold  the  open  end  of  the  bottle  over 
the  ascending  gas.  When  the  water  in  the  bottle  is  replaced 
by  gas,  sink  the  bottle  nearly  to  its  head  in  the  water;  the 
water  will  then  press  upon  the  gas.  Open  the  hole  A  and 
light  the  issuing  gas.  If  sulphuretted  hydrogen  is  present  a 
green  flame  is  seen;  if  carburetted  hydrogen,  a  yellow  lumin- 
ous flame;  if  carbonic  acid  gas,  the  gas  will  not  ignite;  if  these 
gases  are  mixed,  the  flame  will  be  more  or  less  yellow  and 
luminous  in  proportion  to  the  amount  of  carburetted  hydrogen 
present. 

If  carburetted  hydrogen  is  found  it  is  nearly  a  certain  sign 
that  somewhere  in  the  formation  liquid  bitumens  exist, 
although  they  may  be  distant  from  the  place  where  the  gas 
issues. 

All  outcrops  of  the  stratified  rocks  should  be  examined. 
There  are  generally  better  exposures  of  these  rocks  on  the  sides 
of  streams,  canons,  and  gulches  than  elsewhere.  The  surface 
of  the  ground  should  also  be  examined.  If  any  brown  or  black 
material  is  seen  in  the  seams  of  the  rocks  or  saturated  porous 
strata,  the  test  for  bitumens  with  solvents  as  described  herein 
should  be  made. 

If  natural  gas  or  bitumen  is  found  upon  the  surface  of  shale 
there  is  a  strong  probability  that  the  bitumen  has  ascended 
vertically  through  these  rocks  from  porous  strata  below,  as  the 
avenues  for  the  migration  of  the  bitumen  are  usually  seams 
and  cracks  in  the  shale,  the  shale  itself  being  impervious  to 
the  flow  of  the  bitumens,  especially  the  liquid  ones.     But  when 


86 


CALIFORNIA    STATE    MINING    BUREAU. 


porous  sand  is  reached,  or  when  the  outcrop  is  porous  sand,  it 
can  be  presumed  that  the  bitumens  reached  the  surface  through 
the  sand.  Especially  is  this  liable  to  be  true  if  the  sandstones 
stand  at  a  high  angle  with  the  horizon. 

Subsidences  are  indicative  of  the  presence  of  petroleum,  but 
if  any  oil  is  found  in  them  it  will  be  viscous  and  heavy,  the 
fractured  condition  of  the  earth  in  the  subsidence  permitting 
the  escape  of  the  volatile  parts  of  the  oil.  This  is  also  true  of 
burned  shales,  and  if  any  petroleum  exists  in  these  shales  it 
would  be  a  secondary  deposit,  having  entered  the  shales  after 
they  were  burned.     Petroleum  vapor  in  all  probability  assisted 

in  the  burning  of  these  shales. 
As  mineral  waters  always 
accompany  the  bitumens, 
mineral  springs  and  the  evi- 
dences of  former  mineral 
springs  are  to  a  limited  extent 
evidence  of  the  accumulations 
of  the  bitumens.  Selenite, 
travertine,  infusorial  earth, 
and  a  number  of  other  mineral 
deposits  are  evidences  of  for- 
mer mineral  springs.  When 
bitumens  exist  in  a  formation 
they  are  more  often  than 
otherwise  overlaid  with  white 
leached  shales  and  sandstones; 
therefore,  these  rocks  are  an 
indication  of  the  bitumens  to 
a  certain  extent,  and,  owing  to 
their  conspicuous  color,  can  be  seen  from  a  long  distance. 

In  Fig.  27  there  is  represented  a  horizontal  plane  showing 
outcrop  of  a  sand-bearing  petroleum.  The  strike  of  an  anti- 
cline should  not  be  confused  with  the  strike  of  the  strata  or 
outcrop.  The  strike  of  an  anticline  is  its  axis  plane,  shown  by 
C  D  on  this  diagram.  The  strike  of  the  strata  or  outcrop  is 
shown  by  the  lines  G  B  and  G  A.  The  outcrop  may  be  followed 
in  the  directions  shown  by  the  arrows  A  and  B,  and  in  some 
instances  for  a  long  distance,  with  a  liability  of  discovering  oil 
in  the  depths  of  the  dip  of  the  oil  strata,  even  when  bitumens 
are  not  seen  upon  the  surface. 


Fig.  27. 


GENESIS    OF   PETROLEUM    AND    ASPHALTUM. 


87 


So  can  the  apex  of  the  anticline  D  C  be  followed  in  the 
direction  of  the  arrow  C,  and  in  some  instances  for  many  miles, 
with  a  reasonable  expectancy  of  getting  oil  by  drilling  wells, 
even  if  no  bitumens  are  to  be  seen  upon  the  surface;  but  it 
would  be  an  absurdity  to  follow  the  direction  of  the  outcrop 
G  B  and  G  A  in  the  direction  of  E  or  F,  for  the  farther  one 
goes  in  these  directions  the  farther  he  will  be  getting  away 
from  the  petroliferous  strata. 

Therefore,  outcrops  and  anticlines  can  be  followed  from  out- 
side property  into  the  property  being  examined,  and  the  struc- 
ture be  considered  sufficiently  well  demonstrated  so  as  to  justify 
a  person  in  drilling  a  well  for  oil,  even  if  bitumens  were  absent 
from  the  surface  of  the  land  upon  which  the  well  is  to  be  drilled 
and  the  exposures  of  the  strata  are  but  slight.  The  strike  of 
the  anticlines  and  outcrops  can  be  determined  by  a  pocket 
;  ompass. 


5^5^ 


o--m  '■ 


Fig.  28. 

Fig.  28  shows  a  clinometer,  to  be  employed  for  the  determi- 
nation of  the  dip  of  rock  strata  or  the  slopes  of  hillsides.  It 
can  be  readily  made  out  of  stiff  cardboard.  B  is  a  piece  of 
stiff  cardboard  upon  which  is  traced  the  squares  and  numbers 
in  the  manner  shown  in  the  figure.  A  is  a  piece  of  cardboard 
cut  in  the  shape  as  shown  in  diagram.  These  two  pieces  are 
hinged  together  with  the  rivet  C,  this  hinge  permitting  one 
piece  of  cardboard  to  move  upon  the  other.  Care  should  be 
taken  to  see  that  the  upper  edge  of  the  cardboard  A  passes 
through  the  center  of  the  rivet,  and  also  that  the  center  of  the 
rivet  C  is  on  the  upper  and  right-hand  corner  of  the  squares  B. 


88  CALIFORNIA   STATE   MINING    BUREAU. 

A  plumbob  D  is  suspended  from  the  rivet  C,  which  helps  the 
observer  to  keep  the  vertical  lines  of  the  clinometer  vertical. 

When  an  observation  is  made  the  clinometer  is  held  in  the 
manner  shown  in  Fig.  28,  and  while  the  cardboard  B  is  held 
vertical,  which  is  determined  by  the  plumbob  C,  A  is  moved 
upon  B  until  its  dip  agrees  with  the  strata  E  E  (in  Figs.  28 
and  29),  or  other  strata  under  examination.  Considering  that 
each  square  represents  ten  feet  square,  the  readings  of  the  cli- 
nometer would  be  as  follows:  First,  with  the  upper  edge  of  A  on 
line  G;  second,  with  the  upper  edge  of  A  as  represented;  third, 
with  the  upper  edge  of  A  on  line  F. 

Vertical.  Horizontal. 

1 - 20  feet  100  feet 

2 - 56     "  100     " 

3 100     "  45    " 


Fig.  29. 


After  the  observations  are  taken  in  the  field  the  clinometer 
can  be  used  to  draught  the  sectional  views. 

One  use  of  the  clinometer  is  shown  in  Fig.  29.  With  the 
clinometer  the  bituminous  sand  stratum  E  E  is  determined  at 
its  outcrop  A,  and  found  to  be  equal  to  1,000  feet  horizontal 
and  560  feet  vertical,  and  the  slope  of  the  land  is  found  to  be 
1,000  feet  horizontal  to  150  feet  vertical.  The  vertical  depth  of 
the  slope  being  deducted  from  the  vertical  depth  of  the  bitu- 
minous *  stratum  below  B,  shows  that  a  well  to  reach  the 
bituminous  stratum  at  B,  1,000  feet  from  A,  would  have  to  be 
drilled  to  a  depth  of  410  feet.  When  grown  familiar  with  the 
operation  of  this  clinometer,  it  can  be  u6ed  for  many  purposes 
and  different  examinations. 


4fi 


GENESIS   OF    PETROLEUM    AND    ASPHALTUM\  *=^<?^  89 

If  indications  of  the  presence  of  bitumen  are  sufficient  to  jus- 
tify it,  a  topographical  map  of  the  presumed  oil  territory  should 
be  made  before  making  a  cross-section  of  the  rock  structure.  If 
a  person  is  incapable  of  making  a  topographical  map  of  the 
territory,  he  certainly  has  not  the  capacity  of  making  sectional 
views  of  the  same  showing  the  structure,  the  latter  operation 
being  much  more  difficult  and  largely  dependent  upon  the 
former. 

All  indications  should  be  closely  examined  and  thoroughly 
studied.  Even  with  the  greatest  attention  given  to  these  details 
before  selecting  a  place  to  drill  a  well,  there  is  danger  that  the 
lower  parts  of  the  bituminous  strata  encountered  in  the  well 
may  contain  water  in  place  of  gas  and  oil;  or  may  be  calcified 
or  silicified  instead  of  being  bituminized;  or  that  water  has 
entered  the  outcrop  of  the  strata  at  higher  altitudes  and 
ascended  through  the  formation,  floating  the  oil  to  the  surface 
or  carrying  the  same  to  the  other  dip  of  the  anticline. 

Theory  and  observations  cannot  be  perfect,  but  are^  far 
better  than  guessing. 

Somh:  of  the  Fallacies. — Clairvoyants  can  see  as  far  into  a 
millstone  as  any  one,  but  no  farther.  Divining  rods  were  first 
used  to  detect  perjurers,  but  since  liars  have  commenced  to  use 
them  they  have  lost  their  virtue  and  are  of  no  value.  Accumu- 
lations of  fossil  shells  and  bones  are  not  indices  to  deposits  of 
bitumen ;  vast  masses  of  shells  and  bones  exist  where  there  is 
no  petroleum.  The  same  compass-bearing  is  not  applicable  to 
all  deposits  of  oil.  Hardly  any  two  have  the  same  strike,  and 
the  strike  is  frequently  curved.  The  age  of  the  unaltered  rocks 
bears  no  relation  to  the  accumulations  of  bitumen. 

The  mere  geological  age  of  the  unaltered  shales  and  sand- 
stones in  California  does  not  inform  us  of  the  nature  of  these 
rocks;  nor  can  we,  on  the  other  hand,  from  their  petrographic 
character,  arrive  at  the  geological  age  of  these  rocks.  No  kind 
of  unaltered  shale  or  sandstone  is  restricted  to  any  particular 
period. 


7^Bl6 


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